Metastability and high- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>T</mml:mi> <mml:mi>c</mml:mi> </mml:msub> </mml:math> superconductivity in A15-type ternary hydride <mml:math xmlns:mml="http://www.w3.org/1998/Math/

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 <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:msub> <a:mi>YSbH</a:mi> <a:mn>6</a:mn> </a:msub> </a:math> 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 <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:mrow> <b:mi>P</b:mi> <b:mi>m</b:mi> <b:mover accent="true"> <b:mn>3</b:mn> <b:mo>¯</b:mo> </b:mover> </b:mrow> <b:mo> </b:mo> <b:msub> <b:mi>YSbH</b:mi> <b:mn>6</b:mn> </b:msub> </b:math> phase exhibits a predicted critical temperature of 118 K at 50 GPa, among the highest <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"> <d:msub> <d:mi>T</d:mi> <d:mi mathvariant="normal">c</d:mi> </d:msub> </d:math> reported to date for an A15 hydride at this pressure. Thermodynamic analysis shows that <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"> <f:msub> <f:mi>YSbH</f:mi> <f:mn>6</f:mn> </f:msub> </f:math> lies <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"> <g:mrow> <g:mo>∼</g:mo> <g:mn>100</g:mn> <g:mspace width="0.16em"/> <g:mi>meV</g:mi> <g:mo>/</g:mo> </g:mrow> </g:math> 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 <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"> <i:msub> <i:mi>YSbH</i:mi> <i:mn>6</i:mn> </i:msub> </i:math> as a benchmark case illustrating the balance between high- <j:math xmlns:j="http://www.w3.org/1998/Math/MathML"> <j:msub> <j:mi>T</j:mi> <j:mi mathvariant="normal">c</j:mi> </j:msub> </j:math> 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.