Resonant and angle-resolved photoemission measurements were performed
for the non-cuprate layered superconductor Sr2RuO4 (T-c = 0.93 K). Res
onant valence band photoemission spectroscopy shows the existence of a
correlation induced satellite to the main d band across the Ru 4p-4d
threshold Angle-resolved measurements show a surprisingly narrow band
of about 50 meV width and positioned at 26 meV below the Fermi level,
along the Gamma X and Gamma Z directions. This band, arising fom Ru 4d
-O 2p antibonding states is nearly dispersionless over a wide range of
k points about the zone boundary along the Gamma-Z direction (Ru-O di
rection), reminiscent of the extended Van-Hove singularity observed in
the cuprates. The results emphasize the presence of strong correlatio
ns, substantial charge-transfer character to states at the Fermi level
and the existence of a singular dat band near the Fermi-level in this
low T-c layered superconductor, just like the cuprates.