  We study unconventional superconductivity in thin exfoliated single crystals
of a promising 3D topological superconductor candidate, Nb-doped Bi$_2$Se$_3$
through Andreev reflection spectroscopy and magneto-transport. Measurements of
Andreev reflection in low and high resistance samples both show enhanced
conductance around zero bias and conductance dips at the superconducting energy
gap. Such behavior is inconsistent with conventional Blonder-Tinkham-Klapwijk
theory of Andreev reflection. We discuss how our results are consistent with
$p$-wave pairing symmetry, supporting the possibility of topological
superconductivity in Nb-doped Bi$_2$Se$_3$.
