I wish to describe recent results from thermal-Hall conductivity and Nernst experiments on the cuprates**. Quasiparticles (qp) are the basic excitations of the superconducting condensate, but their transport properties are difficult to get at. One way is to measure the thermal Hall conductivity kxy. In high-purity BZO-grown YBaCuO_7, we find that the low-field kxy increases by three orders of magnitude between Tc and 30 K [1]. This corresponds to a striking 100- fold increase in the mean-free-path (mfp). The increase starts abruptly just below Tc, in stark contrast with a recent photoemission result on qp lifetime at the nodes.

In the second part, I report evidence for the existence of vortex-like excitations in LSCO and YBCO (underdoped) at temperatures up to 150 K. I review briefly the idea behind the Nernst experiment, and discuss why it is particularly sensitive to vortex excitations. In LSCO, the vortex-like excitations are detected throughout the phase diagram above Tc, with an onset temperature that is about 1/2 T* (pseudogap temperature) [2]. Results for YBCO are similar provided we compare samples with the same in-plane hole concentration. I will discuss a calibration procedure based on the thermopower vs. T profile.

References
1) Y. Zhang, N. P. Ong, P.W. Anderson, D. A. Bonn, R. Liang, and W. N. Hardy, cond-mat/ 00xxxx.
2) Z. Xu, N. P. Ong, Y. Wang, T. Kakeshita, S. Uchida, Nature 406, 486 (2000).

**Supported by U.S. Office of Naval Research and NSF-DMR MRSEC grant.