Specific heat of lithium ternary borides under magnetic field

Superconductivity in Li₂Pd₃B and Li₂Pt₃B was confirmed at 7.0 K and 2.6 K, respectively. It is clear that their superconductivity is induced by Li addition. Their specific heat was measured under magnetic field by a heat-pulse relaxation method. Those materials have the same cubic structure (P4₃32) composed of distorted octahedrons, whose corners are occupied by Pd/Pt. This structure does not have mirror or inversion symmetry along any directions. Those compounds are very interesting in relation to the symmetry of superconductivity. Sommerfeld (γT) and Debye (βT³) terms of Li₂Pd₃B were given as γ = 8.3 mJ mol^-1 K^-2 and β = 1.4 mJ mol^-1 K^-1. The Debye temperature is θ_D = 202 K. The value of ΔC/γT at T_c was calculated to be 2.1. In the same manner, those parameters were described for Li₂Pt₃B as γ = 9.6 mJ mol^-1 K^-2, β = 0.85 mJ mol^-1 K^-1, θ_D = 240 K, and ΔC/γT_c = 0.75. The superconducting state at zero magnetic field and the normal state achieved after quenching the superconductivity over H_c2 were compared and analyzed to understand the feature of those materials.