Superconductivity and Charge-density-wave-like Transition in Th2Cu4As5

We report the synthesis, crystal structure, and physical properties of a novel ternary compound, Th${}_2$Cu${}_4$As${}_5$. The material crystallizes in a tetragonal structure with lattice parameters $a=4.0716(1)$ Å and $c=24.8131(4)$ Å. Its structure can be described as an alternating stacking of fluorite-type Th${}_2$As${}_2$ layers with antifluorite-type double-layered Cu${}_4$As${}_3$ slabs. The measurement of electrical resistivity, magnetic susceptibility and specific heat reveals that Th${}_2$Cu${}_4$As${}_5$ undergoes bulk superconducting transition at 4.2 K. Moreover, all these physical quantities exhibit anomalies at 48 K, where the Hall coefficient change the sign. These findings suggest a charge-density-wave-like (CDW) transition, making Th${}_2$Cu${}_4$As${}_5$ a rare example for studying the interplay between CDW and superconductivity.