Magnetotransport mechanisms in strongly underdoped YBa2Cu3Ox single crystals -: art. no. 104514

We report magnetoresistivity measurements on strongly underdoped YBa2Cu3Ox (x = 6.25 and 6.36) single crystals in applied magnetic fields H parallel toc axis. We identify two different contributions to both in-plane Delta rho (ab)/rho (ab) and out-of-plane Delta rho (c)/rho (c) magnetoresistivities. The first contribution has the same sign as the temperature coefficient of the resistivity partial derivative ln rho (i)/partial derivativeT (i={c,ab}). This contribution reflects the incoherent nature of the out-of-plane transport. The second contribution is positive, quadratic in field, with an onset temperature that correlates to the antiferromagnetic ordering.