New superconducting superhydride LaCH at relatively low stabilization pressure.

Motivated by the recent experimental discovery of high-temperature carbonaceous sulfur hydride (C-S-H), we have systematically explored the superconductivity of a carbonaceous lanthanum hydride (C-La-H) ternary compound in the pressure range of 50-250 GPa. Based on first-principles calculations and strong-coupling Migdal-Eliashberg theory, we find that a hitherto unreported LaCH ternary system is dynamically and thermally stable above 70 GPa in a clathrate structure with space group 3̄ and exhibits a superconducting critical temperature, , in the range of 69-140 K.