Structure and physical properties of the noncentrosymmetric superconductor Mo3Al2C

We have synthesized polycrystalline samples of the noncentrosymmetric superconductor Mo3Al2C by arc and RF melting, measured its transport, magnetic and thermodynamic properties, and computed its band structure. Experimental results indicate a bulk superconducting transition at T-c similar to 9.2 K while the density of states at the Fermi surface is found to be dominated by Mo d orbitals. Using the measured values for the lower critical field H-c1, upper critical field H-c2, and the specific heat C, we estimated the thermodynamic critical field H-c(0), coherence length xi(0), penetration depth lambda(0), and the Ginzburg-Landau parameter kappa(0). The specific-heat jump at T-c, Delta C/gamma T-c=2.14, suggests that Mo3Al2C is moderately to strongly coupled, consistent with the fast opening of the gap, as evidenced by the rapid release of entropy below T-c from our electronic specific-heat measurements. Above 2 K the electronic specific heat exhibits the power-law behavior, suggesting that synthesis of single crystals and measurements at lower temperature are needed to establish whether the gap is anisotropic. The estimated value of the upper critical field H-c2(0) is close to the calculated Pauli limit, therefore further studies are needed to determine whether the absence of an inversion center results in a significant admixture of the triplet component of the order parameter.