  We present low-temperature magnetoconductance measurements on
Bi$_{1.5}$Sb$_{0.5}$Te$_{1.8}$Se$_{1.2}$ kinks with ribbon-shaped legs. The
conductance displays a clear dependence on the in-plane magnetic field
orientation. The conductance modulation is consistent with orbital
effect-driven trapping of the topological surface states on different side
facets of the legs of the kink, which affects their transmission across the
kink. This magnetic field-driven trapping and conductance pattern can be
explained with a semiclassical picture and is supported by quantum transport
simulations. The interpretation is corroborated by varying the angle of the
kink and analyzing the temperature dependence of the observed
magnetoconductance pattern, indicating the importance of phase coherence along
the cross section perimeter of the kink legs.
