Metastability and high-Tc superconductivity in A15-type ternary hydride YSbH6 at moderate pressure

The discovery of high-temperature superconductors remains a central challenge in materials science. Hydrogen-rich compounds are among the most promising candidates, as they can exhibit phonon-mediated superconductivity at elevated critical temperatures, though their stabilization typically requires extreme pressures. Here, we report the identification of YSbH 6 as a promising superconductor by a multistage high-throughput screening on ternary A15-type hydrides, followed by a high-throughput computational search of the Y-Sb-H system, accelerated by ephemeral data derived potentials. The cubic P m 3 ¯ YSbH 6 phase exhibits a predicted critical temperature of 118 K at 50 GPa, among the highest T c reported to date for an A15 hydride at this pressure. Thermodynamic analysis shows that YSbH 6 lies ∼ 100 meV / atom above the convex hull at 50 GPa, but only 26 meV/atom above the hull at 120 GPa, suggesting possible metastability and synthesis at similar high-pressure conditions. The phase is dynamically stable over a wide pressure range (20–120 GPa), displays kinetic stability at 50 GPa, and elastic stability at 20 and 50 GPa, key ingredients for long-lived metastable behavior at moderate pressures. These results highlight YSbH 6 as a benchmark case illustrating the balance between high- T c performance and limited thermodynamic stability in ternary hydrides, and underscore the importance of combined dynamic, thermodynamic, kinetic, and elastic stability analyses for guiding experimental synthesis of metastable superconductors.