Electron-energy-loss spectroscopy of cleaved single-crystal ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{x}}$

We present the first electron-energy-loss data taken on cleaved single-crystal ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{x}}$. The data confirm in part the results obtained from sintered materials, e.g., on the bulk-plasmon energy. However, the high surface quality and the corresponding better resolution revealed fine structure that requires substantial changes in the interpretation of the spectra.