TURKISH JOURNAL OF MATHEMATICS, cilt.44, sa.6, ss.2306-2311, 2020 (SCI-Expanded)
Let L-n be the free metabelian Leibniz algebra generated by the set X-n = {x(1),..., x(n)} over a field K of characteristic zero. This is the free algebra of rank n in the variety of solvable of class 2 Leibniz algebras. We call an element s(X-n) is an element of L-n symmetric if s(x(sigma(1)),..., x(sigma(n))) = s(x(1),..., x(n)) for each permutation sigma of {1,..., n}. The set L-n(Sn) of symmetric polynomials of L-n is the algebra of invariants of the symmetric group S-n. Let K[X-n] be the usual polynomial algebra with indeterminates from X-n. The description of the algebra K[X-n](Sn) is well known, and the algebra (L-n')(Sn) in the commutator ideal L-n' is a right K[X-n](Sn)-module. We give explicit forms of elements of the K[X-n](Sn)-module (L-n')Sn. Additionally, we determine the description of the group Inn(L-n(Sn)) of inner automorphisms of the algebra L-n(Sn). The findings can be considered as a generalization of the recent results obtained for the free metabelian Lie algebra of rank n.