Spectroscopic Evidence of Kondo-Induced Quasiquartet in ${\mathrm{CeRh}}_2{\mathrm{As}}_2$

${\mathrm{CeRh}}_2{\mathrm{As}}_2$ is a new multiphase superconductor with strong suggestions for an additional itinerant multipolar ordered phase. The modeling of the low-temperature properties of this heavy-fermion compound requires a quartet ${\mathrm{Ce}}^{3+}$ crystal-field ground state. Here, we provide the evidence for the formation of such a quartet state using x-ray spectroscopy. Core-level photoelectron and x-ray absorption spectroscopy confirm the presence of Kondo hybridization in ${\mathrm{CeRh}}_2{\mathrm{As}}_2$. The temperature dependence of the linear dichroism unambiguously reveals the impact of Kondo physics for coupling the Kramer's doublets into an effective quasiquartet. Nonresonant inelastic x-ray scattering data find that the $|{\Gamma }_7^{-}⟩$ state with its lobes along the 110 direction of the tetragonal structure ($xy$ orientation) contributes most to the multiorbital ground state of ${\mathrm{CeRh}}_2{\mathrm{As}}_2$.