Symposium U brought together scientists and engineers working on high efficiency thermal to electric energy conversion technologies to discuss the most recent progress in materials, current theoretical and experimental trends, characterization, and device fabrication. The symposium was designed to emphasize the multi-disciplinary nature (materials science, physics, chemistry and engineering) of the research needed to advance the state-of-the-art technology. Over 175 abstracts were received. This was more than any of the prior thermoelectrics MRS symposia and a strong testament to the continuing interest in this area of study.