We have prepared a new family of rare-earth carbonates, R4(CO3)6(H2O)2en (R=Dy-Lu). With the exception of R=Er, all materials exhibit a steadily decreasing meff below 70K. The Er-containing phase however, exhibits similar behaviour to ca. 10K, below which the moment increases. This together with a saturated moment of 18 muB. per formula unit at 5K suggests that Er4(CO3)6(H2O)2en undergoes ferrimagnetic ordering at low temperatures. We seek to investigate the nature of the magnetic ordering by collecting powder neutron diffraction data at 300, 15 and 2K on a deuterated form of this material. We will also collect data for the non-magnetic Y-containing analogue and for the Ho-containing phase at 300K and 2K. These data will aid in identifying low-structural distortions and allow us to determine whether long-range order is confined to the Er-phase.