  The field of spintronics has seen a surge of interest in altermagnetism due
to novel predictions and many possible applications. MnTe is a leading
altermagnetic candidate that is of significant interest across spintronics due
to its layered antiferromagnetic structure, high Neel temperature (TN ~ 310 K)
and semiconducting properties. We present results on molecular beam epitaxy
(MBE) grown MnTe/InP(111) films. Here, it is found that the electronic and
magnetic properties are driven by the natural stoichiometry of MnTe. Electronic
transport and in situ angle-resolved photoemission spectroscopy show the films
are natively metallic with the Fermi level in the valence band and the band
structure is in good agreement with first principles calculations for
altermagnetic spin-splitting. Neutron diffraction confirms that the film is
antiferromagnetic with planar anisotropy and polarized neutron reflectometry
indicates weak ferromagnetism, which is linked to a slight Mn-richness that is
intrinsic to the MBE grown samples. When combined with the anomalous Hall
effect, this work shows that the electronic response is strongly affected by
the ferromagnetic moment. Altogether, this highlights potential mechanisms for
controlling altermagnetic ordering for diverse spintronic applications.
