  The anomalous Hall effect, commonly observed in metallic magnets, has been
established to originate from the time-reversal symmetry breaking by an
internal macroscopic magnetization in ferromagnets or by a non-collinear
magnetic order. Here we observe a spontaneous anomalous Hall signal in the
absence of an external magnetic field in an epitaxial film of MnTe, which is a
semiconductor with a collinear antiparallel magnetic ordering of Mn moments and
a vanishing net magnetization. The anomalous Hall effect arises from an
unconventional phase with strong time-reversal symmetry breaking and
alternating spin polarization in real-space crystal structure and
momentum-space electronic structure. The anisotropic crystal environment of
magnetic Mn atoms due to the non-magnetic Te atoms is essential for
establishing the unconventional phase and generating the anomalous Hall effect.
