  The electronic interlayer transport of the lightly doped antiferromagnet
La1.79Eu0.2Sr0.01CuO4 has been studied by means of magneto-resistance
measurements. The central problem addressed concerns the differences between
the electronic interlayer coupling in the tetragonal low-temperature (LTT)
phase and the orthorhombic low-temperature (LTO) phase. The key observation is
that the spin-flip induced drop in the c-axis magneto-resistance of the LTO
phase, which is characteristic for pure La2-xSrxCuO4, dramatically decreases in
the LTT phase. The results show that the transition from orthorhombic to
tetragonal symmetry and from collinear to non-collinear antiferromagnetic spin
structure eliminates the strain dependent anisotropic interlayer hopping as
well as the concomitant spin-valve type transport channel. Implications for the
stripe ordered LTT phase of La2-xBaxCuO4 are briefly discussed.
