 The proposed equation for estimating the Lorentz number, L, from the thermo power, S, is an improvement over the current method of using a constant value when detailed band structure and scattering mechanism is unknown. This equation provides a more accurate estimate of the lattice thermal conductivity, cap L, which is important for understanding heat transfer in materials. This article was authored by Hyunsik Kim, Zachary M. Gibbs, Inglutang, and others.