BoltzTraP. A code for calculating band-structure dependent quantities
  A program for calculating the semi-classic transport coefficients is described. It is based on a smoothed Fourier interpolation of the bands. From this analytical representation we calculate the derivatives necessary for the transport distributions. The method is compared to earlier calculations, which in principle should be exact within Boltzmann theory, and a very convincing agreement is found. 
Georg K. H. Madsen, David J. Singh