  Recently, intrinsic antiferromagnetic topological insulator MnBi2Te4 has
drawn intense research interest and leads to plenty of significant progress in
physics and materials science by hosting quantum anomalous Hall effect, axion
insulator state, and other quantum phases. An essential ingredient to realize
these quantum states is the magnetic gap in the topological surface states
induced by the out-of-plane ferromagnetism on the surface of MnBi2Te4. However,
the experimental observations of the surface gap remain controversial. Here, we
report the observation of the surface gap via the point contact tunneling
spectroscopy. In agreement with theoretical calculations, the gap size is
around 50 meV, which vanishes as the sample becomes paramagnetic with
increasing temperature. The magnetoresistance hysteresis is detected through
the point contact junction on the sample surface with an out-of-plane magnetic
field, substantiating the surface ferromagnetism. Furthermore, the non-zero
transport spin polarization coming from the ferromagnetism is determined by the
point contact Andreev reflection spectroscopy. Combining these results, the
magnetism-induced gap in topological surface states of MnBi2Te4 is revealed.
