We have measured the optical properties of the linear-chain compound (
TMTSF)(2)ClO4 and AsF6, in the spin-density-wave state which develops
below T-SDW. In the direction perpendicular to the chains, we observe
clear signatures of the spin-density-wave gap, similar to our previous
findings in the (TMTSF)(2)PF6 compound. (C) 1998 Elsevier Science B.V
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