  In the electronic nematic state, an electronic system has a lower symmetry
than the crystal structure of the same system. Electronic nematic states have
been observed in various unconventional superconductors such as cuprate- and
iron-based, heavy-fermion, and topological superconductors. The relation
between nematicity and superconductivity is a major unsolved problem in
condensed matter physics. By angle-resolved specific heat measurements, we
report bulk quasi-particle evidence of nematicity in the topological
superconductor Sr$_x$Bi$_2$Se$_3$. The specific heat exhibited a clear 2-fold
symmetry despite the 6-fold symmetric lattice. Most importantly, the 2-fold
symmetry appeared in the normal state above the superconducting transition
temperature. This is explained by the angle-dependent Zeeman effect due to the
anisotropic density of states in the nematic phase. Such results highlight the
interrelation between nematicity and unconventional superconductivity.
