Critical-current measurements in epitaxial films of YBa2Cu

We have grown epitaxial films of the ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{x}}$ compound on ${\mathrm{SrTiO}}_{3}$ substrates. The superconducting critical current in these films at 77 K is in excess of ${10}^{5}$ A/${\mathrm{cm}}^{2}$ and at 4.2 K in excess of ${10}^{6}$ A/${\mathrm{cm}}^{2}$.