A new ferromagnetic superconductor: CsEuFe4As4

Superconductivity (SC) and ferromagnetism (FM) are in general antagonistic, which makes their coexistence very rare. Following our recent discovery of robust coexistence of SC and FM in RbEuFe4As4 (Liu et al. in Phys Rev B 93:214503, 2016), here we report another example of such a coexistence in its sister compound CsEuFe4As4, synthesized for the first time. The new material exhibits bulk SC at 35.2 K and Eu2+-spin ferromagnetic ordering at 15.5 K, demonstrating that it is a new robust ferromagnetic superconductor.