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=0.1,0.2,0.3,0.4,0.5x=0.1,0.2,0.3,0.4,0.5). As determined by magnetic, electrical and heat capacity measurements, the superconductivity phase transition temperature TcTc increases with Th concentration to x=0.5(Tc,mid=8.3K). 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, aa, bb, cc and vv 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.