Search for Lorentz violation in short-range gravity
  A search for sidereal variations in the force between two planar tungsten oscillators separated by about 80 microns sets the first experimental limits on Lorentz violation involving quadratic couplings of the Riemann curvature, consistent with no effect at the level of $10^{-7}$ m$^2$. 
J.C. Long and Alan Kostelecky
hep-ex gr-qc hep-ph