A COMBINED KAUP-NEWELL TYPE INTEGRABLE HAMILTONIAN HIERARCHY WITH FOUR POTENTIALS AND A HEREDITARY RECURSION OPERATOR

. We aim to study a Kaup-Newell type matrix eigenvalue problem with four potentials, generated from a specific matrix Lie algebra, and compute an associated soliton hierarchy and its hereditary recursion operator and bi-Hamiltonian structure. The Liouville integrability of the resulting soliton hierarchy is a consequence of the bi-Hamiltonian structure. An illustrative example is explicitly worked out, providing a novel integrable model consisting of combined derivative nonlinear Schr & ouml;dinger equations involving two arbitrary constants.