It is well-known that the orbital effect of the magnetic field suppresses
superconducting Tc. 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 Tc 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.Comment: 6 pages, 4 figures, extended versio