Tests of Lorentz Symmetry with Gravitationally Coupled Atoms

Violations of Lorentz symmetry provide a potential signal for new physics at the Planck scale. At presently accessible energies, these violations are described by the Standard-Model Extension (SME). In this talk I will outline the gravitationally coupled fermion sector of the SME and discuss a new sensitivity to Lorentz violation attainable in atom- interferometer experiments.