Using small-angle neutron scattering we have studied the flux line lattice and the magnetic structure in TmNi2B2C. With an applied field parallel to the crystalline c-axis several magnetic and flux line lattice symmetry transitions have been reported. The subject of this paper is the held-induced magnetic structure and how it is influenced by the flux line lattice symmetry. We find that the domain splitting of the field-induced magnetic structure is hysteretic, and appears to be determined by the history of the flux line lattice symmetry. (C) 1999 Elsevier Science B.V. All rights reserved.