Superconductivity and structural distortion in BaPt${}_2$As${}_2$

We successfully synthesized the BaPt${}_2$As${}_2$ single crystals and studied their structural and physical properties at low temperatures. BaPt${}_2$As${}_2$ crystallizes in the CaBe${}_2$Ge${}_2$-type tetragonal structure (P4/nmm) at room temperature and undergoes a first-order structural transition at $T_S\simeq 275$ K, which is likely associated with a charge-density-wave (CDW) instability. BCS-type superconductivity with two subsequent transitions at $T_{c1}=1.67$K and $T_{c2}$=1.33K are observed in this compound. Thus, BaPt${}_2$As${}_2$ may serve as a new system for studying the interplay of superconductivity and the CDW order.