Comparison of highly-compressedC2/m-SnH₁₂superhydride with conventional superconductors

Satterthwaite and Toepke (1970Phys. Rev. Lett.25741) predicted high-temperature superconductivity in hydrogen-rich metallic alloys, based on an idea that these compounds should exhibit high Debye frequency of the proton lattice, which boosts the superconducting transition temperature,T_c. The idea has got full confirmation more than four decades later when Drozdovet al(2015Nature52573) experimentally discovered near-room-temperature superconductivity in highly-compressed sulphur superhydride, H₃S. To date, more than a dozen of high-temperature hydrogen-rich superconducting phases in Ba-H, Pr-H, P-H, Pt-H, Ce-H, Th-H, S-H, Y-H, La-H, and (La, Y)-H systems have been synthesized and, recently, Honget al(2021arXiv:2101.02846) reported on the discovery ofC2/m-SnH₁₂phase with superconducting transition temperature ofT_c∼ 70 K. Here we analyse the magnetoresistance data,R(T,B), ofC2/m-SnH₁₂phase and report that this superhydride exhibits the ground state superconducting gap of Δ(0) = 9.2 ± 0.5 meV, the ratio of 2Δ(0)/k_BT_c= 3.3 ± 0.2, and 0.010 <T_c/T_F< 0.014 (whereT_Fis the Fermi temperature) and, thus,C2/m-SnH₁₂falls into unconventional superconductors band in the Uemura plot.