Review of 'Evidence for Superconductivity above 260 K in Lanthanum Superhydride at Megabar Pressures'

I would like to note the problems with Figs. 3 and 4 (PRL). In Fig. 3, the difference between the cooling and warming cycles reaches 12-15 K, which is a lot. This was also initially noted by J. Hirsch when analyzing publications on hydrides. This indicates that the cooling rate was very high, and the cooling process itself and the temperature distribution were most likely inhomogeneous. As subsequent studies have shown, such a large difference in the cooling and heating curves is best avoided. Then there will be no questions and a long discussion about what is the T_C of LaH₁₀: 250 K or 260-270 K?

The second remark refers to Fig. 4. It shows that changing the current from 0.1 mA to 10 mA reduces the T_C from 280 K to 257 K. In other words, at 257 K we have a critical current of 10 mA. In such a case, using the standard interpolation formula I_C= I_C(0)*(1-T/T_C)^s, one finds that s= 4. Then the critical current I_C= 2 mA shown in the inset of Fig. 4 for 180 K is clearly not the correct value . At this temperature (180 K), the critical current must be 1000 times greater! And certainly more than 10 mA - the critical current at 257 K. Thus, again questions arise about the correctness of the data presented to support T_C > 250 K in LaH₁₀.