STUDY OF THE ANTIFERROMAGNETIC AND SUPERCONDUCTING PHASE BOUNDARIES IN RBA(2)CU(3)O(6+X) (R=TM, LU) .1. ANISOTROPIC RESISTIVITY ANOMALY AT THE NEEL TEMPERATURE

Precise measurements of the temperature dependences of the in-plane an d out-of-plane resistivity components, rho(ab), rho(c), have been carr ied out on RBa(2)Cu(3)O(6+x) (R = Tm, Lu) single crystals with various oxygen contents. Unusual dome-shape rho(c)(T) dependences with a dist inct maximum at 100-200 K were obtained for all oxygen-deficient (x < 0.5) samples. Non-superconducting crystals demonstrated a considerable anomaly of the out-of-plane resistivity in the temperature range corr esponding to the antiferromagnetic transition. A shape of the anomaly is indicative of the gap formation induced by magnetic ordering. Metal -like temperature dependences of the in-plane resistivity did not chan ge essentially with transition from the superconducting to antiferroma gnetic compositions. No anomaly of the rho(ab)(T) curve was found at t he Neel temperature.