  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.
