Previously studies of the heavy REPtIn alloys (RE = rare earth) have shown a canting of the magnetic moments away from the c-axis. This tilting is still present even with the introduction of external fields up to 5.5 Tesla. The mechanism causing the tilting is still unknown. To obtain more information about the cause of this tilting an experimental investigation of the magnetic properties of these heavy REPtln alloys has been made. A working hypothesis is presented for the model responsible for the canting. This proposes that conduction electrons passing from one rare earth atom to the next pass via the platinum atom. Dzyaloshinsky–Moriya interaction caused by the spin-orbital field of the platinum causes the non-collinear structure. Through measurements of specific heat and magnetism and elastic and inelastic neutron scattering information has been gathered to help to explore this hypothesis and examine the crystal fields which also determine the magnetic properties of these alloys.