Superconductivity with extremely large upper critical fields in Nb(2)Pd(0.81)S(5)

Here, we report the discovery of superconductivity in a new transition metal-chalcogenide compound, i.e. Nb(2)Pd(0.81)S(5), with a transition temperature T(c) ≅ 6.6 K. Despite its relatively low T(c), it displays remarkably high and anisotropic superconducting upper critical fields, e.g. μ(0)H(c2) (T → 0 K) > 37 T for fields applied along the crystallographic b-axis. For a field applied perpendicularly to the b-axis, μ(0)H(c2) shows a linear dependence in temperature which coupled to a temperature-dependent anisotropy of the upper critical fields, suggests that Nb(2)Pd(0.81)S(5) is a multi-band superconductor. This is consistent with band structure calculations which reveal nearly cylindrical and quasi-one-dimensional Fermi surface sheets having hole and electron character, respectively. The static spin susceptibility as calculated through the random phase approximation, reveals strong peaks suggesting proximity to a magnetic state and therefore the possibility of unconventional superconductivity.