  We have performed angle-resolved photoemission spectroscopy (ARPES) on CeBi
which undergoes a two-step antiferromagnetic (AF) transition with temperature.
Soft-x-ray ARPES has revealed the inverted band structure at the X point of
bulk Brillouin zone for CeBi (and also for LaBi) as opposed to LaSb with
non-inverted band structure. Low-energy ARPES on CeBi has revealed the
Dirac-cone band at the Gamma point in the paramagnetic phase associated with
the bulk band inversion. On the other hand, a double Dirac-cone band appears on
entering the first AF phase at T = 25 K, whereas a single Dirac-cone band
recovers below the second AF transition at T = 14 K. The present result
suggests an intricate interplay between antiferromagnetism and topological
surface states in CeBi.
