  We report measurements of the spin polarization (\textbf{\textit{P}}) of the
concentrated magnetic semiconductor EuS using both zero-field and Zeeman-split
Andreev reflection spectroscopy (ARS) with EuS/Al planar junctions. The
zero-field ARS spectra are well described by the modified (spin-polarized) BTK
model with expected superconducting energy gap and actual measurement
temperature (no additional spectral broadening). The fittings consistently
yield \textbf{\textit{P}} close to 80% regardless of the barrier strength.
Moreover, we performed ARS in the presence of a Zeeman-splitting of the
quasiparticle density of states in Al. To describe the Zeeman-split ARS
spectra, we develop a theoretical model which incorporates the solution to the
Maki-Fulde equations into the modified BTK analysis. The method enables the
determination of the magnitude as well as the sign of \textbf{\textit{P}} with
ARS, and the results are consistent with those from the zero-field ARS. The
experiments extend the utility of field-split superconducting spectroscopy from
tunnel junctions to Andreev junctions of arbitrary barrier strengths.
