A method for thermal characterization of a portion of first material of elongate shape on which there is arranged a portion of a second, electrically conductive material of elongate shape, the method including: a) determining characteristic of the portion of second material, b) applying an electric current of angular frequency between ends of the portion of the second material, and measuring the angular frequency harmonic of the electric voltage between these ends for different values of angular frequency, c) calculating coefficient of thermal conductivity of the portion of first material from the values of the harmonic and of the determined characteristic, a width of the portion of the first material being between about 0.9 and 1.1 times the width of the portion of second material, the portion of first material being surrounded by thermal insulation.