Two remarkable articles on the thermoelectric properties of silicon nanowires (and an accompanying News and Views piece by me) appear in today's issue (Jan. 10, 2008) of Nature:

1.    Hochbaum, A. I. et al., Enhanced thermoelectric performance of rough silicon nanowires. Nature 451, 163-167 (2008).
       http://www.nature.com/nature/journal/v451/n7175/abs/nature06381.html
 2.   Boukai, A. I. et al., Silicon nanowires as efficient thermoelectric materials. Nature 451, 168-171 (2008).
       http://www.nature.com/nature/journal/v451/n7175/abs/nature06458.html
3.    Vining, C. B., Desperately seeking silicon. Nature 451, 132-133 (2008).
       http://www.nature.com/nature/journal/v451/n7175/full/451132a.html
4.   see also Editor's Summary: http://www.nature.com/nature/journal/v451/n7175/edsumm/e080110-07.html
     
Long believed useless for thermoelectric energy conversion groups working independently at Stanford and Caltech have measured ZT values near 1 for silicon nanowires at and below room temperature.  Both groups find dramatically lower thermal conductivity values and the Caltech group, working on somewhat smaller nanowires, finds a greatly enhanced Seebeck coefficient due to a 1-D phonon drag effect.

Perhaps we've come to expect thermal conductivity reduction in nanostructures but to see such a large effect in silicon is still new and interesting.  But to see a really large ZT value attributed to phonon-drag is a first and sure to stimulate further work along these lines.

I'm afraid you'll have to get the full articles either from Nature or through your library, but the above links will show you the first paragraph.