Revisiting YH ₉ Superconductivity and Predicting High‐T _<i>c</i> in GdYH ₅

ABSTRACT The discovery of superconductivity in with a critical temperature of approximately has opened a new window toward room temperature superconductivity. In this work, we employ the lowest order constrained variational method to investigate the thermodynamic and magnetic properties of the structure, obtaining results in good agreement with experimental data. Based on the robustness of the LOCV approach for describing high‐ superconductors, we further extend our analysis to the gadolinium–yttrium–hydrogen system across various stoichiometries. The key finding of this study is the prediction of a superconducting phase transition at for under a critical pressure of approximately . This compound crystallizes in a tetragonal structure with space group . Moreover, the calculated gap ratio confirms that is a type‐II superconductor with a critical current density, although practical applications are currently limited by the requirement of high pressure.