  Sub-angstrom Co coverage, being deposited on BiSbTeSe2(0001) surface at
200-330 C, opens a band gap at the Dirac point, with the shift of the Dirac
point position caused by RT adsorbate pre-deposition. Temperature dependent
measurements in 15-150 K range have shown no band gap width change. This fact
indicates the nonmagnetic nature of the gap which may be attributed to the
chemical hybridization of surface states upon the introduction of Co adatoms,
which decrease crystallographic symmetry and eliminate topological protection
of the surface states.
