  We report the electronic structure of a prototypical valence fluctuation
system, YbAl2, using angle-resolved photoemission spectroscopy. The observed
band dispersions and Fermi surfaces are well described in terms of band
structure calculations based on local density approximation. Strong
hybridization between the conduction and 4f bands is identified on the basis of
the periodic Anderson model. The evaluated small mass enhancement factor and
the high Kondo temperature qualitatively agree with those obtained from
thermodynamic measurements. Such findings suggest that the strong hybridization
suppresses band renormalization and is responsible for the valence fluctuations
in YbAl2.
