  We have investigated the structural, magnetic and superconducting properties
of [Nb(1.5nm)/Fe(x)]$_{10}$ superlattices deposited on a thick Nb(50nm) layer.
Our investigation showed that the Nb(50nm) layer grows epitaxially at
800$^\circ$C on Al$_2$O$_3$(1$\bar{1}$02) substrate. Samples grown at this
condition posses a high residual resistivity ratio of 15-20. By using neutron
reflectometry we show that Fe/Nb superlattices with $x<$ 4 nm form a
depth-modulated FeNb alloy with concentration of iron varying between 60% and
90%. This alloy has properties of a weak ferromagnet. Proximity of this weak
ferromagnetic layer to a thick superconductor leads to an intermediate phase
that is characterized by co-existing superconducting and normal-state domains.
By increasing the thickness of the Fe layer to $x$ = 4 nm the intermediate
phase disappears. We attribute the intermediate state to proximity induced
non-homogeneous superconductivity in the periodic Fe/Nb structure.
