  Effective models focused on pertinent low-energy degrees of freedom have
substantially contributed to our qualitative understanding of quantum
materials. An iconic example, the Kondo model, was key to demonstrating that
the rich phase diagrams of correlated metals originate from the interplay of
localized and itinerant electrons. Modern electronic structure calculations
suggest that to achieve quantitative material-specific models, accurate
consideration of the crystal field and spin-orbit interactions is imperative.
This poses the question of how local high-energy degrees of freedom become
incorporated into a collective electronic state. Here, we use resonant
inelastic x-ray scattering (RIXS) on CePd$_3$ to clarify the fate of all
relevant energy scales. We find that even spin-orbit excited states acquire
pronounced momentum-dependence at low temperature - the telltale sign of
hybridization with the underlying metallic state. Our results demonstrate how
localized electronic degrees of freedom endow correlated metals with new
properties, which is critical for a microscopic understanding of
superconducting, electronic nematic, and topological states.
