Electrical properties of high-$T_c$ superconducting single-crystal ${\mathrm{Eu}}_1{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_y$

The normal resistivity and $H_{c2\mathrm{}}$ of single-crystal ${\mathrm{Eu}}_1{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_y$ with $T_c=95\mathrm{}$ K and transition width of 0.25 K were measured. The crystal has orthorhombic and twinning structure with the $a$ and $b$ axes interchanged. $H_{c2\mathrm{}}$ shows anisotropic characteristics, the ratio of ${\left(\frac{d{H}_{c2\mathrm{}}}{\mathrm{dT}}\right)}_{T_c}$ between the $c$ axis and the $a-b$ plane is about 4, and $H_{c2\mathrm{}}\mathrm{}\left(0\right)\mathrm{}$ is large, estimated to be 190 T. The ${\mathrm{Eu}}_1{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_y$ behaves as a quasi-two-dimensional superconductor. It is unambiguously evident in the temperature dependence of the normal resistivity that $\frac{d\rho }{\mathrm{dT}}$ is anomalously large and that the temperature-dependent curve has a bulge shape.