  Rietveld analysis of the powder X-ray diffraction of a new layered
oxyarsenide, LaNiOAs, which was synthesized by solid-state reactions, revealed
that LaNiOAs belongs to the tetragonal ZrCuSiAs-type structure (P4/nmm) and is
composed of alternating stacks of La-O and Ni-As layers. The electrical and
magnetic measurements demonstrated that LaNiOAs exhibits a superconducting
transition at 2.4 K, and above this, LaNiOAs shows metallic conduction and
Pauli paramagnetism. The diamagnetic susceptibility measured at 1.8 K
corresponded to ~20% of perfect diamagnetic susceptibility, substantiating that
LaNiOAs is a bulk superconductor.
