metals

fact: there are no high conductivity (ie; 90+ % IACS) alloys that are also hard(ish) or strong(ish).

Beryllium copper is often used where a hard conductive alloy is called for, or phosphor bronze.
Both have lousy conductivity compared to plain old copper, and the former is not something you want to machine, because the dust is carcinogenic.

"Reasonable" conductivity - say 50% - 70% IACS - that isn't nearly as good as copper but is at least better than say, iron, is fine for most applications, where the currents are relatively low.

What a shame that I don't deal in low current applications, at least not hobby-wise.

When the amps are in the tens of thousands or higher, you start paying attention to the conductivity of your alloys.

If you don't, Bad Things can happen, such as rapid disassembly of non-moving components.

When the conducting volume is high, you don't care either. For instance, the collecting plates of my pulser, which connect the six pulse caps together, are made of 1/4" aluminum sheet. Dunno the alloy, but I'd bet lunch that it's garden-variety 6061-T6, and that's 40% IACS. But there is so much of it, it just cannot possibly matter.

Unfortunately, what I need a high strength & high conductivity alloy for is a small volume part that willy have a great deal of current (10,000 - 100,000 amps) passing through it, albeit for very short times.

There is no good solution, really.

Well.

If what I do were easy, everyone would do it.

And we can't have that.