  In this study, we investigate the electronic structure of a spin-triplet
superconductor candidate CeRh$_2$As$_2$ using high-resolution angle-resolved
photoemission spectroscopy and density functional theory calculations. Notably,
Fermi surface nesting hints at connections to magnetic excitation or quadrupole
density wave phenomena, elucidating the superconducting mechanisms. Measured
band structures reveal primarily localized 4f electrons, with minor itinerant
contributions. Additionally, a transition from localized to itinerant behavior
and significant c-f hybridization anisotropy underscore the role of f-electrons
in shaping electronic properties. These findings deepen our understanding of
CeRh$_2$As$_2$'s unconventional superconductivity and magnetism. Further
exploration promises advances in superconductivity research.
