Unusual transport and strongly anisotropic thermopower in PtCoO2 and PdCoO2

Phys Rev Lett. 2010 Apr 30;104(17):176601. doi: 10.1103/PhysRevLett.104.176601. Epub 2010 Apr 28.


We show, using Boltzmann transport calculations and analysis of experimental data, that hexagonal PdCoO2 and PtCoO2 have a highly unusual metallic transport. The in-plane transport is typical of a very good metal, with high conductivity and low positive thermopower. The c-axis transport is completely different, with 2 orders of magnitude lower, but still coherent, conductivity and remarkably a very large negative thermopower. This large anisotropy of the thermopower provides an opportunity for investigating transport in a highly unusual regime using bulk materials.