The crystal of a (ethylenedioxytetrathiafulvalenoquinone-1,3-diselenolemethide, 1)2 center dot FeBr4 center dot(1,2-dichloroethane, DCE)(1/2) salt obtained by electrochemical oxidation of 1 in DCE containing a supporting electrolyte, NBU4 center dot FeBr4, exhibits metallic conductivity down to 0.45 K. The negative magnetoresistance of the electrical resistance (11) in the conducting ab -plane suggests stronger interactions between the d spins of the FeBr4- ions and the conducting Pi electrons than those in the FeCl4- salt of the corresponding 1,3-dithiolemethide donor molecule. The d spins order antiferromagnetically at 4.5 K, the highest temperature obtained so far in antiferromagnetic molecular metals with significant Pi-d interactions.