Analysis of the Possible Influence of Crystallographic Shear Planes on Magnetic and Superconducting Behavior in ${\rm RuSr}_{2}{\rm EuCu}_{2}{\rm O}_{8}$

We present results of High-resolution Transmission Electron Microscopy (HRTEM), and of the electrical and magnetic properties with various magnetic fields applied in bulk sample of EuSr 2 RuCu 2 O 8 . Our data suggest that crystallographic shear planes observed by transmission electron microscopy could be originating the anomalies observed in the magnetic and electric measurements. These defects constitute a discontinuity in the Ru-O charge reservoir layers forming anti-phase boundaries, with big amounts of Eu between Ru layers locally deficient in O.