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I. Bonalde, H. Kim, R. Prozorov, C. Rojas, P. Rogl, E. Bauer:
"Evidence for conventional superconducting behavior in noncentrosymmetric Mo₃Al₂C";
Physical Review B, 84 (2011), 134506; S. 1 - 4.

We report on measurements of the magnetic penetration depth of polycrystalline samples of nonmagnetic Mo3Al2C (Tc=9 K) without inversion symmetry. Two previous specific-heat measurements in this compound found different anomalous peaks in the low-temperature limit. One of these peaks was attributed to the superconducting transition at 3 K of the impurity phase Mo2C. We argue here that the second anomalous peak may be caused by the superconducting transition of SiC:Al at 1.45 K, another impurity phase possibly present in Mo3Al2C samples. The temperature-independent behavior of the penetration depth observed below 0.5 K is taken as firm evidence for the presence of a nodeless superconducting gap in Mo3Al2C. Numerical calculations using the BCS expression for the penetration depth give qualitative support for an isotropic energy gap in Mo3Al2C. The present results suggest that Mo3Al2C is a conventional s-wave superconductor, although two-gap or anisotropic-gap superconductivity cannot be ruled out.

http://dx.doi.org/10.1103/PhysRevB.84.134506