  We investigate the subgap transport properties of a S-F-Ne structure. Here S
(Ne) is a superconducting (normal) electrode, and F is either a ferromagnet or
a normal wire in the presence of an exchange or a spin- splitting Zeeman field
respectively. By solving the quasiclassical equations we first analyze the
behavior of the subgap current, known as the Andreev current, as a function of
the field strength for different values of the voltage, temperature and length
of the junction. We show that there is a critical value of the bias voltage V *
above which the Andreev current is enhanced by the spin-splitting field. This
unexpected behavior can be explained as the competition between two-particle
tunneling processes and decoherence mechanisms originated from the temperature,
voltage and exchange field respectively. We also show that at finite
temperature the Andreev current has a peak for values of the exchange field
close to the superconducting gap. Finally, we compute the differential
conductance and show that its measurement can be used as an accurate way of
determining the strength of spin-splitting fields smaller than the
superconducting gap.
