A few weeks ago I noted the recent discovery of some new quaternary iron-based superconductors which might be of interest for thermoelectrics.  David Bérardan tells me his group had already initiated studies and have a paper currently in the "early view" section of physica status solidi (RRL):

Loreynne Pinsard-Gaudart, D. B. J. B. N. D. Large Seebeck coefficients in iron-oxypnictides: a new route towards n-type thermoelectric materials. physica status solidi (RRL) - Rapid Research Letters 9999, NA (2008).

No thermal conductivity or ZT data yet, but the authors are enthusiastic that good ZT values can be obtained around liquid nitrogen temperatures.

A free e-print version is available from http://arxiv.org using this link:

http://arxiv.org/pdf/0806.2751