Electronic Structure in High Temperature Superconducting Oxides

We have performed measurements on entwined single crystals of YBCO using both photoemission and positron angular correlation of annihilation radiation and on single crystals of LSCO using only angular correlation. Fermi surface features in good agreement with band theory were found and identified in all of the measurements. In photoemission the Fermi momentum was fixed for several points and the band dispersion below the Fermi energy was mapped. In positron angular correlation measurements the shape of the Fermi surface was mapped for the CuO chains (YBCO) and the CuO planes (LSCO). Demonstration of the existence of Fermi surfaces in the HTSC materials points a direction for future theoretical considerations.