Conventional isotropic s-wave superconductivity with strong electron-phonon coupling in Sc5Rh6Sn18

Sc5Rh6Sn18 is a diamagnetic metallic compound (space group: I4(1)/acd, a approximate to 13.5 angstrom, c approximate to 27.1 angstrom) which becomes superconducting (sc) at T-c = 5.15 K. The sc state was studied on single-crystal samples by temperature-and field-dependent electrical resistivity, specific heat, and muon-spin rotation (mu SR) spectroscopy. No anisotropy of the upper critical field B-c2 = 7.75 T is observed. Analyses of specific heat indicate enhanced values of the jump [Delta(cp)/(gamma(tot) = 1.58] and of the energy gap ratio [Delta(0)/(k(B)T(c)) = 2.39] as well as an exponential decrease of the electronic contribution below T-c/2. Together with the saturation of the superfluid density for T < 3 K observed by mu SR spectroscopy these findings lead us to classify Sc5Rh6Sn18 as a moderately strong coupled isotropic s-wave superconductor. However, above T-c, the crystals reveal a surprisingly anisotropic and large resistivity of 2.5-4.5 m Omega m with metalliclike behavior perpendicular to the c axis and by a factor of similar to 2 larger parallel to c, which decreases upon increasing temperature. These observations are discussed in connection to a characteristic intrinsic disorder in the crystal structure ofSc(5)Rh(6)Sn(18).