  We investigate the electronic structure of $2H$-$\mathrm{Nb}\mathrm{S}_2$ and
$h$-$\mathrm{BN}$ by angle-resolved photoemission spectroscopy (ARPES) and
photoemission intensity calculations. Although in bulk form, these materials
are expected to exhibit band degeneracy in the $k_z=\pi/c$ plane due to screw
rotation and time-reversal symmetries, we observe gapped band dispersion near
the surface. We extract from first-principles calculations the near-surface
electronic structure probed by ARPES and find that the calculated photoemission
spectra from the near-surface region reproduce the gapped ARPES spectra. Our
results show that the near-surface electronic structure can be qualitatively
different from the bulk one due to partially broken nonsymmorphic symmetries.
