  X-ray absorption (XAS) and Resonant Inelastic X-ray Scattering (RIXS) spectra
of LaPt$_2$Si$_2$ single crystal at the Si L and La N edges are presented. The
data are interpreted in terms of density functional theory, showing that the Si
spectra can be described in terms of Si $s$ and $d$ local partial density of
states (LPDOS), and the La spectra are due to quasi-atomic local $4f$
excitations. Calculations show that Pt $d$-LPDOS dominates the occupied states,
and a sharp localized La $f$ state is found in the unoccupied states, in line
with the observations.
