In a recent article, Tran et al. [Phys. Rev. B 78, 172505 (2008)] reported results from muon-spin-rotation (μSR) measurements of an Mo3Sb7 superconductor. Based on the analysis of the temperature and the magnetic field dependences of the Gaussian relaxation rate, σsc, it was suggested that Mo3Sb7 is a superconductor with two isotropic s-wavelike energy gaps. This relates to results found previously in the specific-heat measurements by several of the same authors in Acta Mater. 56, 5694 (2008). The purpose of this Comment is to point out that from the analysis made by Tran et al., the presence of two superconducting energy gaps in Mo3Sb7 cannot be justified. The analysis of μSR data does not account for the reduction in σsc with increasing temperature. The specific-heat data can be satisfactorily described within the framework of the one-gap model by assuming the presence of a small residual specific-heat component. The experimental data of Tran et al., as well as our earlier published μSR results [Phys. Rev. B 78, 014502 (2008)], all seem to be consistent with the presence of single isotropic superconducting energy gap in Mo3Sb7.
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