  We study the role of electron correlations among Co 3d electrons contributing
to the conduction band of a Kondo lattice compound, Ce2CoSi3, using high
resolution photoemission spectroscopy and ab initio band structure
calculations. Experimental results reveal signature of Ce 4$f$ states derived
Kondo resonance feature at the Fermi level and dominance of Co 3d contributions
at higher binding energies in the valence band. The line shape of the
experimental Co 3$d$ band is found to be significantly different from that
obtained from the band structure calculations within the local density
approximations. Consideration of electron-electron Coulomb repulsion among Co
3d electrons leads to a better representation of experimental results. The
correlation strength among Co 3$d$ electrons is found to be about 3 eV.
Signature of electron correlation induced satellite feature is also observed in
the Co 2p core level spectrum. Thus, these results demonstrate the importance
of the electron correlation among conduction electrons to derive the
microscopic description of such Kondo systems.
