Resonant photoelectron diffraction (RPED) and its use for studies of lanthanides are presented. To demonstrate the potential of this technique, we show how the ground-state properties of the heavy-fermion compound YbRh2Si2 and its trivalent counterpart YbCo2Si2 can be determined from RPED measurements and modeling. By providing a modeling recipe and exploring RPED capabilities and limitations, we anticipate wide applications of this method for insights into the properties of lanthanide-based systems.