Magnetoresistivity measurements of the vortex liquid phase of single crystals, with various angles between unidirected twins and the current direction, were performed in magnetic fields of up to 12T. It was found that unidirected twin planes were the cause of an anisotropic pinning of the vortices. In contrast with measurements of the usual longitudinal magnetoresistance of isotropic samples, which was even with respect to reversal of the magnetic field direction, an additional contribution to the longitudinal resistivity was observed which was odd with respect to reversal of the magnetic field. This was attributed to the presence of unidirected twins in the crystals.

Experimental Observation of a New Galvanomagnetic Effect in YBaCuO Single Crystals with Unidirected Twins. V.V.Chabanenko, A.A.Prodan, V.A.Shklovskij, A.V.Bondarenko, M.A.Obolenskii, H.Szymczak, S.Piechota: Superconductor Science and Technology, 1998, 11[10], 1133-6