  The calculations of electronic transport coefficients and optical properties
require a very dense interpolation of the electronic band structure in
reciprocal space that is computationally expensive and may have issues with
band crossing and degeneracies. Capitalizing on a recently developed
pseudo-atomic orbital projection technique, we exploit the exact tight-binding
representation of the first principles electronic structure for the purposes of
(1) providing an efficient strategy to explore the full band structure
$E_n({\bf k})$, (2) computing the momentum operator differentiating directly
the Hamiltonian, and (3) calculating the imaginary part of the dielectric
function. This enables us to determine the Boltzmann transport coefficients and
the optical properties within the independent particle approximation. In
addition, the local nature of the tight-binding representation facilitates the
calculation of the ballistic transport within the Landauer theory for systems
with hundreds of atoms. In order to validate our approach we study the
multi-valley band structure of CoSb$_3$ and a large core-shell nanowire using
the ACBN0 functional. In CoSb$_3$ we point the many band minima contributing to
the electronic transport that enhance the thermoelectric properties; for the
core-shell nanowire we identify possible mechanisms for photo-current
generation and justify the presence of protected transport channels in the
wire.
