Anisotropic in-plane thermal conductivity of single-crystal

We report measurements of the in-plane thermal conductivity (Formula presented) of (Formula presented) (Y-124) single crystals in the temperature range (Formula presented) and compare them with previous results on (Formula presented) (Y-123). For transport perpendicular to the CuO chains, (Formula presented) W/mK, and along the chains, (Formula presented) W/mK. The temperature dependence of (Formula presented) for both transport directions is much stronger than in (Formula presented) (Y-123), indicative of substantially superior lattice heat conduction in Y-124, and resulting in maximum values for (Formula presented) at (Formula presented) K exceeding 200 W/mK. The data imply a surprisingly large anisotropy in the lattice conduction. (Formula presented) and (Formula presented) are enhanced in the superconducting state as in other cuprates. The magnitude and anisotropy of the enhancement are discussed and compared to those of Y-123.