The structure and magnetostriction of the high-prcontent(Tb(0.2)Pr(0.8))(Fe(0.4)Co(0.6))(1.88-x)C(0.05)B(x) (0 <= x <= 0.08) alloys homogenized at 700 degrees C for 7 days have been investigated by X-ray diffraction and magnetic measurement. It was found that the matrix of the (Tb(0.2)Pr(0.8))(Fe(0.4)Co(0.6))(1.88-x)C(0.05)B(x) alloys belongs to (Tb, Pr) (Fe, Co, C, B)(2) phase with MgCu(2)-type structure. The Curie temperatures are derived from M-T curves, which showed a slight increase when 0 <= x <= 0.06, then decreases with further increasing x. The composition dependence of magnetostriction lambda(a) (= lambda(parallel to) - lambda(perpendicular to)) for (Tb(0.2)Pr(0.8))(Fe(0.4)Co(0.6))(1.88-x)C(0.05)B(x) alloys reaches a maximum value at x = 0.01 at room temperature. The double split (440) lines of the Laves phase overlap gradually with increasing x and finally approach to form a broadened peak for x = 0.03. The spontaneous magnetostriction lambda(111) decreases with increasing boron contents. (C) 2011 Elsevier B.V. All rights reserved.