A self-energy formalism for determining the quasiparticle band structure of the Hubbard systems is deduced. The self-energy is obtained from the dynamically screened Coulomb interaction whose bare value is the correlation energy U. A method for integrating the Schrödingerlike equation with the self-energy operator is given. The method is applied to the cubic Laves phase of -CeAl2 because it is a clear Hubbard system with a very complex electronic structure and, moreover, this system provides us with sufficient experimental data for testing our method. © 1990 The American Physical Society.