Superconductivity in LiGa₂Ir Heusler type compound with VEC = 16

Polycrystalline LiGa₂Ir has been prepared by a solid state reaction method. A Rietveld refinement of powder x-ray diffraction data confirms a previously reported Heusler-type crystal structure (space group Fm-3m, No. 225) with lattice parameter a = 6.0322(1) Å. The normal and superconducting state properties were studied by magnetic susceptibility, heat capacity, and electrical resistivity techniques. A bulk superconductivity with T_c = 2.94 K was confirmed by detailed heat capacity studies. The measurements indicate that LiGa₂Ir is a weak-coupling type-II superconductor ([Formula: see text]_e-p = 0.57, [Formula: see text]C/[Formula: see text]T_c = 1.4). Electronic structure, lattice dynamics, and the electron-phonon interaction are studied from first principles calculations. Ir and two Ga atoms equally contribute to the Fermi surface with a minor contribution from Li. The phonon spectrum contains separated high frequency Li modes, which are seen clearly as an Einstein-like contribution in the specific heat. The calculated electron-phonon coupling constant [Formula: see text]_e-p = 0.68 confirms the electron-phonon mechanism for the superconductivity. LiGa₂Ir and recently reported isoelectronic LiGa₂Rh are the only two known representatives of the Heusler superconductors with the valence electron count VEC = 16.