Superconductivity in CeBeH8 and CeBH8 at moderate pressures

High-pressure structural searches of superhydrides CeBeH8 and CeBH8 were performed under ambient pressure up to 300 GPa. We identify F m 3 ‾ m -CeBeH8 with a superconducting transition temperature T c of 56 K at 10 GPa. Two more phases with spacegroup R 3 ‾ m and C 2 / m , were investigated within the increasing pressures. CeBH8 shows a similar phase transition process as CeBeH8 but with higher transition pressures and higher T c . F m 3 ‾ m -CeBH8 is predicted to be superconducting above 120 GPa with a maximum T c of 118 K at 150 GPa. R 3 ‾ m -CeBH8 and C 2 / m -CeBH8 are dynamically stable above 120 GPa and 100 GPa, respectively. The maximum T c is 123 K at 195 GPa for R 3 ‾ m -CeBH8, and 115 K at 350 GPa for C 2 / m -CeBH8. Our work enriches the family of ternary hydrides and may provide a useful guideline for further search for superconducting hydrides at low and moderate pressures.