An ingot plate (10) made of a crystallized cleaveable thermoelectric material, said plate having substantially parallel opposed upper and lower faces (11,12), opposed longitudinal end faces (13), and opposed side faces (14),
- characterized in that said plate is of a layered structure having substantially parallel cleavage planes (X1 to Xn;
- Y1 to Yn), that substantially all of said cleavage planes appearing in said opposed end faces are disposed at a first cleavage angle of not more than 26.4.degree. with respect to said upper and lower faces, and that substantially all of said cleavage planes appearing in said side faces are disposed at a second cleavage angle of not more than 10.degree. with respect to said upper and lower faces.