It's not that straightforward if you have a bunch of samples which may only contain a small fraction of the material which isn't connected together. Firstly it

It's not that straightforward if you have a bunch of samples which may only contain a small fraction of the material which isn't connected together. Firstly it becomes very difficult to probe a small grain that is hopefully pure and secondly you can't just dump an arbitrary amount of current through a superconductor, they only have zero resistance below a critical current level, and for LK-99 even if it was superconducting this was thought to be quite low, so a small sample means a very small voltage drop even for a normal conductor.