  We experimentally study magnetization reversal curves for MnTe single
crystals, which is the altermagnetic candidate. Above 85~K temperature, we
confirm the antiferromagnetic behavior of magnetization $M$, which is known for
$\alpha$--MnTe. Below 85~K, we observe anomalous low-field magnetization
behavior, which is accompanied by the sophisticated $M(\alpha)$ angle
dependence with beating pattern as the interplay between $M(\alpha)$ maxima and
minima: in low fields, $M(\alpha)$ shows ferromagnetic-like 180$^\circ$
periodicity, while at high magnetic fields, the periodicity is changed to the
90$^\circ$ one. This angle dependence is the most striking result of our
experiment, while it can not be expected for standard magnetic systems. In
contrast, in altermagnets, symmetry allows ferromagnetic behavior only due to
the spin-orbit coupling. Thus, we claim that our experiment shows the effect of
weak spin-orbit coupling in MnTe, with crossover from relativistic to
non-relativistic net magnetization, and, therefore, we experimentally confirm
altermagnetism in MnTe.
