New radical cation salt BDA-TTP [2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathia-pentalene] with iodomercurate anion of the (BDA-TTP)(4)Hg2I6 composition has been synthesized. X-ray analysis at 100 K revealed the alternation of conducting donor layers of the beta-type and inorganic layers composed of the [Hg2I6](2-) anions. The compound shows a semiconducting temperature dependence of resistivity and the temperature activation dependence of spin susceptibility.