Superconductivity in the Th-doped Y NiC2 compounds

We have observed superconductivity in the two-phase samples with nominal compositions (Y 1−xThx)NiC2 ( x = 0.1 , 0.2 , 0.3 , 0.4 , 0.5 ). As determined by magnetic, electrical and heat capacity measurements, the superconductivity phase transition temperature T c increases with Th concentration to x = 0.5 ( T c , mid = 8.3 K ) . Powder X-ray diffraction data provide the evidence for bulk superconductivity in an orthorhombic CeNiC2-type majority fraction of the sample volume while the minor impurity phase ThC2 has no effect on the superconductivity. The variation of room temperature lattice parameters, a , b , c and v of these substitutional intermetallic samples indicates the systematic substitution of Y 3+ ions by Th4+ ions irrespective of the existence of the 2nd impurity phase.