Gravitational Tests of Lorentz Symmetry with Atoms

Violations of Lorentz symmetry provide a potential signal for new physics at the Planck scale. ~At our present energy scales, general Lorentz violation is described by the Standard-Model Extension (SME). ~In this talk, I will give an outline of the fermion sector of the SME and describe a new sensitivity to Lorentz violation that is attainable in experiment, arising from gravitational interactions with atoms.