  Electrical resistivity \rho(T) of the 5f ferromagnet UGa2 was investigated
for single-crystal samples as a function of pressure and magnetic field. The
Curie temperature monotonously increases from T$_{C}$ = 124 K under
quasi-hydrostatic pressure up to 154 K at p = 14.2 GPa, after which it turns
down steeply and reaches T$_{C}$ = 147 K at p = 15.2 GPa. At 20 GPa the
compound is already non-magnetic. This dramatic variation is compatible with
exchange interactions mediated by the 5f hybridization with the non-f states.
The external pressure first enhances the exchange coupling of the 5f moments,
but eventually suppresses the order by washing out the 5f moments. Such a
two-band model is adequate for the weakly delocalized 5f states. The
spin-disorder resistivity, which produces very high \rho-values (300
\mu\Omega.cm) is gradually suppressed by the pressure. In the paramagnetic
state, this leads to a crossover from initial negative to positive d\rho/dT.
