  Invariant theory provides more efficient tools, such as Molien generating
functions and integrity bases, than basic group theory, that relies on
projector techniques for the construction of symmetry--adapted polynomials in
the symmetry coordinates of a molecular system, because it is based on a finer
description of the mathematical structure of the latter. The present article
extends its use to the construction of polynomial bases which span possibly,
non--totally symmetric irreducible representations of a molecular symmetry
group. Electric or magnetic observables can carry such irreducible
representations, a common example is given by the electric dipole moment
surface. The elementary generating functions and their corresponding integrity
bases, where both the initial and the final representations are irreducible,
are the building blocks of the algorithm presented in this article, which is
faster than algorithms based on projection operators only. The generating
functions for the full initial representation of interest are built recursively
from the elementary generating functions. Integrity bases which can be used to
generate in the most economical way symmetry--adapted polynomial bases are
constructed alongside in the same fashion. The method is illustrated in detail
on XY4 type of molecules. Explicit integrity bases for all five possible final
irreducible representations of the tetrahedral group have been calculated and
are given in the supplemental material associated with this paper.
