  The spin-polarized surface states of topological insulators have attracted
interest both from a fundamental and applied point of view. A recent proposal
describes a method of probing these surface states with ferromagnetic contacts,
which was subsequently applied to a variety of materials. In this study, we use
this method on the potential topological insulator SmB$_6$ with a new design
based on the Corbino geometry. Though the signal behaves as predicted for all
orientations of current and magnetic field, its magnitude is much larger than
expected. Possible parasitic effects such as stray field-induced Hall voltages
are excluded, leaving the origin of the observations uncertain. This
corroborates the need for careful analysis when interpreting results of similar
experiments.
