Formerly, I was a chemist/material scientist producing conductors, resistors, dielectrics, encapsulants for the electronics industry. Some of our customers are highly esteemed hi - end audio companies.
Palladium(Pd) was one component which was included in many of our conductors and resistors. It is one of the 8 precious metals(Silver, Gold, Platinum, Palladium, Osmium, Ruthenium, Iridium, and Rhodium). In the mid 1990's, the cost of Pd ranged from about $70 - $100 per troy ounce (31.1 g/oz as opposed to the typical avoirdupois ounce where 28.8 g = 1 ounce). Then, the cost spiked. It reached $1000 per troy ounce.
I developed a product line of lightning arrestor resistors(0.1 Ohm to 100 Ohms, I think the company extended the line upward since I have left) which used a Pd/silver(Ag) alloy. Normally, Pd is alloyed with Ag to produce what(along with Ag/Platinum(Pt) and Ag/Pt/Pd) are the highest quality conductors and resistors. By the way, a resistor is just a conductor with a higher level of resistance.
Alloying Pd and Ag yields many benefits. This alloy is especially immune to oxidation, corrosion, and almost any form of deterioration. These forms of deterioration take place as a result of exposure to various other compounds, like oxygen, sulfur, acids, etc.; heat; high voltage(like a lightning strike); in other words, the ravages of time. We are all aware how silver and copper degrade over time.
Also, the Temperature Coefficient of Resistance(TCR) of metals themselves is highly positive(eg: +3500). This means as temperature rises, so does resistance. Conversely, the TCR of nonmetals(ceramics, glass, etc.) is highly negative(eg: -3500). In this case, as temperature rises, resistance drops. The goal, of course is to have a TCR of 0, where resistance is unaffected by temperature.
The ideal alloy of Pd and Ag is 55/45, and is one of the few instances where 0 TCR, or close to it can be achieved. There is another low point for TCR(memory has faded, maybe +40?) with a 25/75 Pd/Ag alloy, which is much cheaper.
0 TCR is desired in electrical components(thermistors excepted, of course - temperature is calculated via their change in resistance), and almost always pays dividends in the long run. Most equipment and the components that are used to build this equipment are designed to operate at specific temperature and electrical conditions. Fluctuating TCR guarantees that the electrical conditions fluctuate. 0 TCR protect components from the damaging surge which occurs during equipment turn on. The reason behind this is that since metals are normally highly positive in terms of TCR, when a component is cold the resistance is much lower than it will be during its normal operating temperature. In audio equipment, I would think it would very desirable in circuits, conductors, resistors, etc.
For the record, Palladium is a good conductor. I'll assume that the data that Bwhite has provided is accurate, but that will only prove my point. Resistivity/Conductivity is compared in terms of orders of magnitude. For example, each product in a conductor or resistor product would be one order of magnitude greater than the next. The figures above show that Pd is within an order of magnitude. When we talk about metals, they are all basically good conductors; it's one of the definitions of a metal. Move to semi - conductors(from hundreds of KOhms into MOhms), and we can begin to talk about things which are not good conductors. They are many, many, many orders of magnitude higher in resistance(like going from -3 to +6 or more). After that would be insulators, where there is no conductivity.
I believe the point he was making is that relative resistivity is not a good barometer of good sound, which I wholeheartedly agree with. Impurities, both in level and type, I would think would be far more critical. While one could assert that an alloy is in itself an impure material, I would counter that with if the Pd and Ag are pure, and the alloy's content does not contain anything other than trace quantities of other elements, it CAN be considered "pure".
Further, to those hung up on resistivity, the alloying of Pd/Ag would guarantee a lower resistance in the long run than silver(converting to silver oxide) if the material was at all subject to change in resistance(which is normally the case). Pd/Ag would be several orders of magnitude more conductive than silver oxide.
Also, Pd/Ag is much easier to solder, and takes to the process in a much more friendly regard than pure silver. That could translate into many things chemically(I am sure someone at a place like DuPont has analyzed this via AA, X - Ray, EDAX, Flame - IPC, etc.), which I am sure have sonic correlation. I have always felt that the solder joint was a focal point of sonic degradation. Nasty things must be going on during the process. If the joint can be improved(less impurities, lower thermal shock, decreased degradation, formation of something closer to the theoretical eutectic) via the starting material, I would think we would reap benefit in the audio world.
Sonically, I have not had the opportunity to listen to cables containing Pd. But, in the opinions of most materials scientists, Pd always improves silver, other than the areas of cost and increased resistance of the virgin material(when that is even an issue).
Hope I didn't bother too many out there with all this babble...
