High-resolution electron-energy-loss spectroscopy of YBa2Cu

High-resolution electron-energy-loss spectroscopy has been performed for a polycrystalline sample of YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/ in the temperature range between 300 and 45 K. A pronounced surface-conductivity transition is observed between 100 and 200 K both via the inelastically and elastically scattered electrons.