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 noncollinear 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 nonmagnetic Te atoms is essential for establishing the unconventional phase and generating the anomalous Hall effect.

Charles University Faculty of Mathematics and Physics Ke Karlovu 3 121 16 Prague 2 Czech Republic

Departamento de Fisica y Geociencias Universidad del Norte Barranquilla 080020 Colombia

Department of Physics University of Konstanz 78457 Konstanz Germany

Institut für Physik Johannes Gutenberg Universität Mainz 55128 Mainz Germany

Institute of Physics Academy of Sciences of the Czech Republic Cukrovarnická 10 162 00 Praha 6 Czech Republic

Institute of Semiconductor and Solid State Physics Johannes Kepler University Linz Altenbergerstr 69 4040 Linz Austria

Institute of Solid State and Materials Physics Technical University Dresden 01062 Dresden Germany

Leibniz Institute of Solid State and Materials Research Helmholtzstr 20 01069 Dresden Germany

School of Physics and Astronomy University of Nottingham Nottingham NG7 2RD United Kingdom

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