  We present ab initio electronic structure calculations based on density
functional theory for the thermoelectric properties of Bi$_2$Te$_3$ films.
Conductivity and thermopower are computed in the diffusive limit of transport
based on the Boltzmann equation. Bulk and surface contribution to the transport
coefficients are separated by a special projection technique. As a result we
show clear signatures of the topological surface state in the thermoelectric
properties.
