Enhanced superconductivity in ThNiAsN

We report the synthesis and physical properties of a nickel-based arsenide ThNiAsN. The new compound crystallizes in a ZrCuSiAs-type structure (space group P4/nmm ) with lattice parameters a=4.0804(4) \AA and c=7.9888(6) \AA . Bulk superconductivity at T_c =4.3 \text{K} is demonstrated by the measurements of electrical resistivity, dc magnetic susceptibility, and heat capacity. The upper critical field at zero temperature, H_c2(0) , and the specific-heat jump at T _c are 6.1 T and 40 \text{mJ} \cdot \text{K}^-1\cdot \text{mol}^-1 , respectively. These two physical quantities, together with the T _c value, are the highest among the Ni-based ZrCuSiAs-type materials. We discuss this enhanced superconductivity in terms of the internal chemical pressure in ThNiAsN.