  In this work we study a two-band model of a superconductor in a square
lattice. One band is narrow in energy and includes local Coulomb correlations
between its quasi-particles. Pairing occurs in this band due to nearest
neighbor attractive interactions. Extended s-wave, as well as d-wave symmetries
of the superconducting order parameter are considered. The correlated electrons
hybridize with those in another, wide conduction band through a k-dependent
mixing, with even or odd parity depending on the nature of the orbitals. The
many-body problem is treated within a slave-boson approach that has proved
adequate to deal with the strong electronic correlations that are assumed here.
Since applied pressure changes mostly the ratio between hybridization and
bandwidths, we can use this ratio as a control parameter to obtain the phase
diagrams of the model. We find that for a wide range of parameters, the
critical temperature increases as a function of hybridization (pressure), with
a region of first-order transitions. When frustration is introduced it gives
rise to a stable superconducting phase. We find that superconductivity can be
suppressed for specific values of band-filling due to the Coulomb repulsion. We
show how pressure, composition and strength of correlations affect the
superconductivity for different symmetries of the order parameter and the
hybridization.
