  The coupling between electrons and phonons in solids plays a central role in
describing many phenomena, including superconductivity and thermoelecric
transport. Calculations of this coupling are exceedingly demanding as they
necessitate integrations over both the electron and phonon momenta, both of
which span the Brillouin zone of the crystal, independently. We present here an
ab initio method for efficiently calculating electron-phonon mediated transport
properties by dramatically accelerating the computation of the double integrals
with a dual interpolation technique that combines maximally localized Wannier
functions with symmetry-adapted plane waves. The performance gain in relation
to the current state-of-the-art Wannier-Fourier interpolation is approximately
2n_s \times M, where n_s is the number of crystal symmetry operations and M, a
number in the range 5 - 60, governs the expansion in star functions. We
demonstrate with several examples how our method performs some ab initio
calculations involving electron-phonon interactions.
