  We present scanning tunneling microscopy and spectroscopy studies around an
individual excess Fe atom, working as a local perturbation, in the parent
material of the iron-chalcogenide superconductor Fe$_{1+\delta}$Te.
Spectroscopic imaging reveals a novel isosceles triangular electronic structure
around the excess Fe atoms. Its spatial symmetry reects the underlying
bicollinear antiferromagnetic spin state and the structural monoclinic
symmetry. These findings provide important clues to understand the role of the
excess Fe atoms, which complicate the understanding of the phenomena occurring
in iron-chalcogenide materials.
