  The long-sought Majorana fermion is expected to manifest in a
topological-superconductor heterostructure as a zero bias conductance peak
(ZBCP). As one promising platform for such heterostructures, we investigate the
cleaved surface of the topological semimetal Sb(111) using scanning tunneling
microscopy and spectroscopy. Remarkably, we find a robust ZBCP on some terraces
of the cleaved surface, although no superconductor is present. Using
quasiparticle interference imaging, Landau level spectroscopy and density
functional theory, we show that the ZBCP originates from a van Hove singularity
pushed up to the Fermi level by a sub-surface stacking fault. Amidst the sprint
to stake claims on new Majorana fermion systems, our finding highlights the
importance of using a local probe together with detailed modeling to check
thoroughly for crystal imperfections that may give rise to a trivial ZBCP
unrelated to Majorana physics.
