  Synchrotron-based angle-resolved photoemission spectroscopy is used to
determine the electronic structure of layered SnSe, which was recently turned
out to be a potential thermoelectric material. We observe that the top of the
valence band consists of two nearly independent hole bands, whose tops differ
by ~20 meV in energy, indicating the necessity of a multivalley model to
describe the thermoelectric properties. The estimated effective masses are
anisotropic, with in-plane values of 0.16-0.39 m$_0$ and an out-of-plane value
of 0.71 m$_0$, where m$_0$ is the rest electron mass. Information of the
electronic structure is essential to further enhance the thermoelectric
performance of hole-doped SnSe.
