During the study of the Nd-Ni-Mg system we already discovered two new ordered Mg-rich phases: NdNiMg5 and NdNiMg15. For both compounds antiferromagnetic transitions are observed at TN = 12 K et 9 K, respectively. From the value of the Curie constants it appears that Ni atoms carry a small magnetic moment (the main contribution arises from Nd atoms). The Nd and Ni atoms form infinite ordered graphite-type layers in NdNiMg5, and infinite linear chains in NdNiMg15. For both compounds we observe a complex magnetic behavior on the M vs H curves with multiple meta-magnetic transitions below TN. In order to understand this behavior we would like to solve the magnetic structure of these intermetallics at zero field at first. We believe that this could be related to the peculiar dimensionality of the magnetic network of Nd and Ni atoms.