Synthesis of superconducting phase of La_0.5Ce_0.5H₁₀ at high pressures

Clathrate hydride Fm (3) over barm-LaH10 has been proven as the most extraordinary superconductor with the critical temperature T-c 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 T-c value of the specific phase in LaH10. However, strong structural instability distorts Fm (3) over barm structure and leads to a rapid decrease of Tc at low pressures. Here, we investigate the phase stability and superconducting behaviors of Fm (3) over barm-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 Fm (3) over barm-La0.5Ce0.5H10 in the pressure range of 140-160 GPa. Superconductivity with T-c 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.