Ternary Superhydrides Under Pressure of Anderson's Theorem: Near-Record Superconductivity in (La, Sc)H12

Lanthanum-hydrogen system and its derivatives hold significant promise for achieving room-temperature superconductivity. In this study, the formation of ternary lanthanum-scandium superhydrides is examined at pressures up to 220 GPa. The primary product of the LaSc alloy's reaction with hydrogen is a newly discovered cubic (La,Sc)H₁₂, demonstrating a clear superconducting transition in all six channels of the van der Pauw-contact scheme at 244–248 K. In this compound with an unusually large unit-cell volume, virtually no magnetoresistance is observed in fields up to 68 Tesla. Synthesized samples of (La,Sc)H₁₂ demonstrate pronounced superconducting diode and SQUID-like effects at a record high temperature of 233 K, which opens up prospects for the use of superhydrides in compact electronics. Furthermore, the analysis reveals the possible formation of a lower hexagonal polyhydride (La,Sc)H_6-7, which can potentially account for the drop in electrical resistance observed near 274 K. This anomaly between 265–290 K also appears in the radio-frequency transmission measurements and may be of a superconducting nature.