Summarizing https://arxiv.org/pdf/2307.12008.pdf

Here's my try:

The authors report the first room-temperature ambient-pressure superconductor with a modified lead-apatite structure. They synthesized LK-99 and proved its superconductivity by measuring critical temperature, zero resistivity, critical current, critical magnetic field, and Meissner effect. The superconductivity originates from a slight volume shrinkage caused by Cu2+ substitution of Pb2+(2) ions in the insulating network of Pb(2)-phosphate, which generates stress and creates superconducting quantum wells in the interface. The heat capacity results indicate that the new model is suitable for explaining the superconductivity of LK-99.

The authors also measured the external magnetic field (H) dependence of applied current, DC magnetization value, and critical current value to confirm the superconducting phase still exists under 10 Oe up to 400 K. They explain the non-uniform resistivity of the bulk samples as inter-grain boundaries, intergranular vortex flow, free vortex flow of polycrystalline superconducting phase. Additionally, they observed Josephson-like phenomenon in the form of a dc voltage drop across the sample when it is subjected to an ac magnetic field. The authors suggest that LK-99 could be used for various applications such as high-temperature superconductors, quantum computing, and spintronic devices.