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. 
W. B. Jiang, C. Y. Guo, Z. F. Weng, Y. F. Wang, Y. H. Chen, Y. Chen,   G. M. Pang, T. Shang, X. Lu and H. Q. Yuan
cond-mat.supr-con