The characterization of a twin-free orthorhombic crystal was described. A tetragonal single crystal was grown by crystal pulling, and was annealed in an O atmosphere under uniaxial compression in order to prevent twin formation. The resultant crystal had a twin-free structure. The critical temperature of the crystal was about 91.8K and the critical current was only some 20% of that of the twinned crystal at 1T.

H.Kutami, Y.Yamada, S.Koyama, J.G.Wen, T.Egi, Z.Nakagawa, Y.Shiohara: Japanese Journal of Applied Physics - 1, 1997, 36[2], 674-5