  We apply the slave-boson approach of Kotliar and Ruckenstein to the two-band
Hubbard model with an Ising like Hund's rule coupling and bands of different
widths. On the mean-field level of this approach we investigate the Mott
transition and observe both separate and joint transitions of the two bands
depending on the choice of the inter- and intraorbital Coulomb interaction
parameters. The mean-field calculations allow for a simple physical
interpretation and can confirm several aspects of previous work. Beside the
case of two individually half-filled bands we also examine what happens if the
original metallic bands possess fractional filling either due to finite doping
or due to a crystal field which relatively shifts the atomic energy levels of
the two orbitals. For appropriate values of the interaction and of the crystal
field we can observe a a band insulating state and a ferromagnetic metal.
