Reflection symmetry at a B=0 metal-insulator transition in two   dimensions
  We report a remarkable symmetry between the resistivity and conductivity on opposite sides of the B=0 metal-insulator transition in a two-dimensional electron gas in high-mobility silicon MOSFET's. This symmetry implies that the transport mechanisms on the two sides are related. 
D. Simonian, S. V. Kravchenko, and M. P. Sarachik (City College of the   City University of New York)