Investigation of normal and superconducting states in noncentrosymmetric Re24Ti5

We report a detailed characterization of the noncentrosymmetric superconductor Re24Ti5 using powder x-ray diffraction (XRD), magnetic susceptibility, electrical resistivity, thermal conductivity, Seebeck coefficient, and specific heat measurements. Rietveld refinement of powder XRD data confirms that Re24Ti5 crystallizes in the alpha-Mn structure. All measured quantities demonstrate a bulk superconducting transition at T-c = 5.8 K. Our low-temperature specific heat data measured down to 0.5 K yield a Sommerfeld coefficient gamma = 111.8 mJ mol(-1) K-2, which implies a high density of states at the Fermi level. Moreover, the electronic specific heat in the superconducting state was found to obey a typical s-wave expression, revealing a single gap Delta/k(B) = 10.6 K. This value gives a ratio of 2D/k(B)T(c) = 3.68, higher than the value of 3.5 predicted from BCS theory. On this basis, we conclude that the noncentrosymmetric Re24Ti5 compound can be characterized as a moderately coupled BCS-type superconductor. Furthermore, the obtained parameters from the present study of Re24Ti5 were compared to those of the isostructural compound Re23.8Nb5.2, indicating the similarity between both systems.