Synthesis of superconducting phase of La0.5Ce0.5H10 at high pressures

Clathrate hydride Fm3ˉm -LaH10 has been proven as the most extraordinary superconductor with the critical temperature Tc above 250 K upon compression of hundreds of GPa in recent years. A general hope is to reduce the stabilization pressure and maintain the high Tc value of the specific phase in LaH10. However, strong structural instability distorts Fm3ˉm structure and leads to a rapid decrease of Tc at low pressures. Here, we investigate the phase stability and superconducting behaviors of Fm3ˉm -LaH10 with enhanced chemical pre-compression through partly replacing La by Ce atoms from both experiments and calculations. For explicitly characterizing the synthesized hydride, we choose lanthanum-cerium alloy with stoichiometry composition of 1:1. X-ray diffraction and Raman scattering measurements reveal the stabilization of Fm3ˉm -La0.5Ce0.5H10 in the pressure range of 140–160 GPa. Superconductivity with Tc of 175 ± 2 K at 155 GPa is confirmed with the observation of the zero-resistivity state and supported by the theoretical calculations. These findings provide applicability in the future explorations for a large variety of hydrogen-rich hydrides.