Some remarks on possible superconductivity of composition Pb${}_9$CuP${}_6$O${}_{25}$

A material called LK-99, a modified-lead apatite crystal structure with the composition Pb${}_{10-x}$Cu${}_x$(PO${}_4$)${}_6$O ($0.9<x<1.1$) has been reported to be an above-room-temperature superconductor at ambient pressure. It is hard to expect that it will be straightforward for other groups to reproduce the original results. We provide here some remarks which may be helpful for a success.