Superconductivity at 7.8 K in the ternary LaRu2As2 compound

Here we report the discovery of superconductivity in the ternary LaRu2As2 compound. The polycrystalline LaRu2As2 samples were synthesized by the conventional solid state reaction method. Powder X-ray diffraction analysis indicates that LaRu2As2 crystallizes in the Th Cr2Si2-type crystal structure with the space group I4/mmm（No. 139）, and the refined lattice parameters are a = 4.182（6）  and c = 10.590（3） . The temperature dependent resistivity measurement shows a clear superconducting transition with the onset Tc（critical temperature） at 7.8 K, and zero resistivity happens at 6.8 K. The upper critical field at zero temperature μ0Hc2（0） was estimated to be 1.6 T from the resistivity measurement. DC magnetic susceptibility measurement shows a bulk superconducting Meissner transition at 7.0 K, and the isothermal magnetization measurement indicates that LaRu2As2 is a type-II superconductor.