Seebeck coefficient of the structurally one-dimensional material, TIInSe2, known as a p-type conductor, has been measured in the temperature range 70 degrees C to 500 degrees C in vacuum by using four probe techniques. At temperatures above 200 degrees C this coefficient is found to be negative. With temperature down to below 200 degrees C, the coefficient is becoming positive and huge to a cutting-edge value of 10(7)mu V/degrees C. The obtained results are discussed in terms of an incommensurate superlattice phase, which might have taken place in TIInSe2 at temperatures below 200 degrees C, and led to the above unique thermoelectric properties of this material. It is expected that thermoelectric devices based on TllnSe(2) will have superior parameters. (c) 2005 Elsevier B.V All rights reserved.