REDUCED RESISTIVITY ANISOTROPY RATIO IN BI2SR2CACU2O8 SINGLE-CRYSTALSSHOWING ZERO RESISTANCE AT 97-K

In this article, we report resistivity results on single crystals of B i-2212 with a composition very close to the standard one and with a Sr /Ca ratio close to 2. We confirm the metallic temperature dependence o f rho(c) that has been recently noted by other authors, and report a r oom-temperature resistivity ratio, rho(c)/rho(ab), of the order of 170 , a rather small value, indicative of good metallic behaviour. In addi tion, we find an anomaly in the resistivity-versus-temperature curves, centered around 240 K. We also report a T(c)(0) as high as 97 K, the highest T(c)(0) reported so far for Bi-2212. Apart from the 240 K anom aly which remains to be clearly understood, the other observations are tentatively interpreted in terms of band theory and of the interlayer coupling in these samples.