Enhanced Superconductivity in Th 2 Mo 2 Ru 2 Si 4 C with a Collapsed Intergrowth Structure

Abstract We report the discovery of bulk superconductivity in a new quinary intermetallic compound Th 2 Mo 2 Ru 2 Si 4 C, crystallized in a collapsed 22241-type structure. This structure is characterized by the intergrowth of ThMo 2 Si 2 C and ThRu 2 Si 2 units interconnected by equivalent Si-Si bonds that enhance inter-sublattice coupling. The refined lattice parameters are a = 4.2212(1) Å and c = 20.3899(7) Å. Electrical resistivity and magnetic susceptibility measurements of both polycrystalline and single-crystal samples consistently demonstrate bulk superconductivity with a transition temperature T c ∼ 6.0 K significantly higher than those of the constituent compound ThMo 2 Si 2 C and its related analogs. Under magnetic fields, the superconducting state exhibits a nearly isotropic behavior, which is attributed to strong covalent interlayer coupling. First-principles calculations reveal a substantial contribution from the Mo-d orbitals near the Fermi level, which exhibit several band-crossing points. The enhancement in T c can be attributed to the synergistic combination of the valence electron concentration and the inter-sublattice self-doping effect between the [Ru 2 Si 2 ] and [Mo 2 Si 2 C] layers.