Superconductivity and multiple pressure-induced phases in BaPt$_2$As$_2$
  The newly discovered BaPt$_2$As$_2$ shows a structural distortion at around 275~K, followed by the emergence of superconductivity at lower temperatures. Here we identify the presence of charge density wave (CDW) order at room temperature and ambient pressure using single crystal x-ray diffraction, with both a superlattice and an incommensurate modulation, where there is a change of the superlattice structure below $\simeq$ 275~K. Upon applying pressure, BaPt$_2$As$_2$ shows a rich temperature-pressure phase diagram with multiple pressure-induced transitions at high temperatures, the emergence or disappearance of which are correlated with sudden changes in the superconducting transition temperature $T_c$. These findings demonstrate that BaPt$_2$As$_2$ is a promising new system for studying competing interactions and the relationship between high-temperature electronic instabilities and superconductivity. 
C. Y. Guo, W. B. Jiang, M. Smidman, F. Han, C. D. Malliakas, B. Shen,   Y. F. Wang, Y. Chen, X. Lu, M. G. Kanatzidis, H. Q. Yuan
cond-mat.supr-con cond-mat.str-el