Lk. Montgomery et al., SYNTHESIS, SUPERCONDUCTIVITY, X-RAY STRUCTURE AND ELECTRONIC BAND-STRUCTURE OF LAMBDA-(BETS)(2)GACL4, Physica. C, Superconductivity, 219(3-4), 1994, pp. 490-496
The first superconductor derived from bis(ethylenedithio)tetraselenafu
lvalene (BETS), lambda-(BETS)(2)GaCl4, possesses a relatively sharp re
sistive transition with an onset of about 7.5 K and a midpoint of 6 K.
Several samples had much broader transitions with higher onsets (> 9
K). Superconductivity was confirmed by AC susceptibility (midpoint 4.5
K, Delta T = 1 K). lambda-(BETS)(2)GaCl4 crystallizes in the monoclin
ic space group P ($) over bar 1, with four BETS units stacked in a zig
-zag fashion in the unit cell. Tight-binding band calculations suggest
that lambda-(BETS)(2)GaCl4 has both 1-D and 2-D Fermi surfaces, the m
ost prominent feature being a closed hole pocket centered at X account
ing for similar to 33% of the first Brillouin zone. These results conf
irm and extend the recent findings of Kobayashi and coworkers.