  It is well-known that the orbital effect of the magnetic field suppresses
superconducting $T_c$. We show that for a system, which is in the
Larkin-Ovchinnikov-Fulde-Ferrell (FFLO) state at zero external magnetic field,
the orbital effect of an applied magnetic field can lead to the enhancement of
the critical temperature higher than $T_c$ at zero field. We concentrate on two
systems, where the in-plane FFLO-state was predicted recently. These are
equilibrium S/F bilayers and S/N bilayers under nonequilibrium quasiparticle
distribution. However, it is suggested that such an effect can take place for
any plane superconducting heterostructure, which is in the in-plane FFLO-state
(or is close enough to it) at zero applied field.
