  The occupied and the unoccupied electronic structure of CeAg$_2$Ge$_2$ single
crystal has been studied using high resolution photoemission and inverse
photoemission spectroscopy respectively. High resolution photoemission reveals
the clear signature of Ce $4f$ states in the occupied electronic structure
which was not observed earlier due to the poor resolution. The coulomb
correlation energy in this system has been determined experimentally from the
position of the $4f$ states above and below the Fermi level. Theoretically the
correlation energy has been determined by using the first principles density
functional calculations within the generalized gradient approximations taking
into account the strong intra-atomic (on-site) interaction Hubbard $U_{eff}$
term. Although the valence band calculated with different $U_{eff}$ does not
show significant difference, but the substantial changes are observed in the
conduction band. The estimated value of correlation energy from both the theory
and the experiment is $\approx$4.2~eV for CeAg$_2$Ge$_2$.
