They measured the resistivity of a pure Cu2S sample, a sample S1 containing 95% LK-99 and 5% Cu, and a sample S2 containing 30% LK-99 and 70% Cu2S.
The resistivity of the Cu2S sample has a drop of 3 to 4 orders of magnitude at about 390K (when temperature decreases). In the S2 sample the drop is much smaller, only factor 5. In S1 there is no such drop. Here the resistivity always falls with increasing temperature.
Then they write in the conclusion: "The superconducting-like behavior in LK-99 most likely originates from a magnitude reduction in resistivity caused by the first-order structural phase transition of Cu2S."
Since resistivity drop in LK-99 with temperature is about factor 10 according to https://arxiv.org/pdf/2307.12037.pdf Fig 5, that would mean that Sukbae Lee et al's specimen was composed of more than 70% Cu2S, which is unlikely.
The resistivity drop with decreasing temperature is not the only "superconducting-like behavior in LK-99". There is also a resistivity drop with decreasing current density and magnetic field at constant temperature. That cannot be explained with a phase change.
The resistivity of the Cu2S sample has a drop of 3 to 4 orders of magnitude at about 390K (when temperature decreases). In the S2 sample the drop is much smaller, only factor 5. In S1 there is no such drop. Here the resistivity always falls with increasing temperature.
Then they write in the conclusion: "The superconducting-like behavior in LK-99 most likely originates from a magnitude reduction in resistivity caused by the first-order structural phase transition of Cu2S."
Since resistivity drop in LK-99 with temperature is about factor 10 according to https://arxiv.org/pdf/2307.12037.pdf Fig 5, that would mean that Sukbae Lee et al's specimen was composed of more than 70% Cu2S, which is unlikely.
The resistivity drop with decreasing temperature is not the only "superconducting-like behavior in LK-99". There is also a resistivity drop with decreasing current density and magnetic field at constant temperature. That cannot be explained with a phase change.