Superconductivity in Th_<b>3</b>Ni_<b>3</b>Sn_<b>4</b>

Abstract

Specific heat, resistivity and ac- and dc-magnetic susceptibility measurements revealed that Th 3 Ni 3 Sn 4 is a new superconductor with the transition temperature T c =1.38 K. The electronic specific heat coefficient γ is 31.1 mJ/K 2 mol-f.u., the Debye temperature Θ D is 255 K and the electron-phonon coupling constant λ ep is 0.43. The upper critical field H c2 determined by ac-susceptibility in magnetic fields follows the temperature dependence calculated by Helfand and Werthamer. We conclude that Th 3 Ni 3 Sn 4 is a BCS-superconductor of type-II with the GL parameter κ=10. Both susceptibility enhancement probably due to spin fluctuation and anomalous temperature dependence of the resistivity suggest that the conduction electrons with d -character play an essential role in the superconductivity.