Physical properties of the noncentrosymmetric superconductor Nb0.18Re0.82

We report the synthesis and measurements of magnetic, transport, and thermal properties of polycrystalline Nb0.18Re0.82, which has a superconducting transition at Tc similar to 8.8 K. The noncentrosymmetric alpha-Mn structure of the compound is confirmed by x-ray diffraction. Using the measured values for the lower critical field H-c1, upper critical field H-c2, and the specific heat C, we estimate 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 = 1.86, suggests that Nb0.18Re0.82 is a moderately coupled superconductor. Below T-c the electronic specific heat decays exponentially, suggesting that the gap is isotropic. Our data suggest that the triplet admixture is weak in the polycrystalline form of compound. However, the estimated value of the upper critical field H-c2(0) is close to the calculated Pauli limit.