de Haas-van Alphen frequencies and upper critical field anisotropy in Nb3Sn

de Haas-van Alphen frequencies in the (100) and (110) planes of Nb3Sn have been measured with a typical accuracy of 1%. Several frequency branches have been found between 100 and 1000 T. Effective masses corresponding to some of the orbits at symmetry directions have been estimated from the experiments. A pronounced anisotropy ( approximately 10%) in the upper critical field was observed. The magnitude of the critical field was found to be sample dependent. The DHVA data are interpreted using self-consistent new ASW band-structure calculations which include tetragonal distortion of the unit cell.