  We have performed micro-focused angle-resolved photoemission spectroscopy on
NdSb which exhibits the type-I antiferromagnetism below TN = 16 K. We succeeded
in selectively observing the band structure for all three types of single-q
antiferromagnetic (AF) domains at the surface. We found that two of the three
surfaces whose AF-ordering vector lies within the surface plane commonly show
twofold symmetric surface states (SSs) around the bulk-band edges, whereas the
other surface with an out-of-plane AF-ordering vector displays fourfold
symmetric shallow electronlike SS at the Brillouin-zone center. We suggest that
these SSs commonly originate from the combination of the PT (space-inversion
and time-reversal) symmetry breaking at the surface and the band folding due to
the AF order. The present results pave a pathway toward understanding the
relationship between the symmetry and the surface electronic states in
antiferromagnets.
