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 θD = 202 K. The value of ΔC/γT at Tc 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, θD = 240 K, and ΔC/γTc = 0.75. The superconducting state at zero magnetic field and the normal state achieved after quenching the superconductivity over Hc2 were compared and analyzed to understand the feature of those materials.