We report the synthesis and characterization of a new ternary molybdenum pnictide superconductor, Cs2Mo3As3. The powder x-ray diffraction analysis reveals the quasi-one-dimensional (Q1D) hexagonal crystal structure formed by Cs+ and infinite (Mo3As3)2− chains as indicated by the wire-like grain morphology. Electrical resistivity and magnetic susceptibility characterizations exhibit superconductivity with the onset transition temperature at 11.5 K, which is the highest in all Q1D superconductors reported so far. An upper critical magnetic field of about 61.7 T at zero temperature was extrapolated from the resistivity measurement under a magnetic field, which is much higher than the Pauli paramagnetic limit, and the reason for such a high upper critical field may lie in its unconventional nature of superconducting pairing symmetry. The discovery of Cs2Mo3As3 inspires the search for new superconductors for future high field applications.
