  The bulk tin selenide (SnSe) is the best thermoelectric material currently
with the highest figure-of-merit due to the strong phonon-phonon interactions.
We investigate the effect of electron-phonon coupling (EPC) on the transport
properties of two-dimensional (2D) SnSe sheet. We demonstrate that EPC plays a
key role in the scattering rate where the constant relaxation time
approximation is deficient. The EPC strength is especially large in contrast to
that of pristine graphene. The scattering rate depends sensitively on the
system temperatures and the carrier densities when the Fermi energy approaches
the band edge. We also investigate the magnetothermoelectric effect of the 2D
SnSe. It is found that at low temperatures there are enormous magnetoelectrical
resistivity and magnetothermal resistivity above 500\%, suggesting the high
potential for device applications. Our results agree reasonably well with the
experimental data.
