Discovery of magnetic phase transitions in heavy-fermion superconductor CeRh$_2$As$_2$

We report on the specific heat studies performed on a new generation of CeRh$_2$As$_2$ single crystals. Superior quality of the samples and dedicated experimental protocol allowed us to observe an antiferromagnetic-like behavior in the normal state and to detect the first-order phase transition of magnetic origin within the superconducting state of the compound. Although in the available literature the physical behavior of CeRh$_2$As$_2$ is most often described with the use of quadrupole density wave scenario, we propose an alternative explanation using analogies to antiferromagnetic heavy-fermion superconductors CeRhIn$_5$ and Ce$_2$RhIn$_8$.