PURPOSE: To provide a polymeric composition of high electric conductivity having an excellent formability and mechanical strength by adding oxidative dopant to a silicon-containing highpolymer compound containing ester compound.

CONSTITUTION: The principal chain of the composition has an Si-Si bond and/or C-C multiple bond formed from polysilanes, polymerides of disilanylene phenylene series, and polymerides of disilanylene ethynylene series, and the general equation of the compound is expressed by Eqs. I and II. In Eqs., R1-R4 represent one-valent hydrocarbonic radical having an H or a C number 1-10 and A represents a phenylene radical in the o-, m-, or p-position, acetylene radical of -C≡C-, etc. The ester compound is carboxylic esters and phosphoric esters as expressed by Eqs. III and IV. In Eqs., R5, R6 are one-valent hydrocarbonic radical having a C number 1-20 of the same sort or a plurality of sorts or one-valent hydrocarbonic radical substituted with hetero radical such as O, N while R8 has C number 1-6, wherein the condition h>3 should be met. As the oxidative dopant I or triiron tetroxide is used, and addition is performed by dry or wet method, while hexane, ether, etc., is used simultaneously as an inert solvent.