(Ge/Sn)*

The recent discovery of Anomalous Hall Effect in Mn₃X (X=Sn,Ge) suggests the existence of Weyl nodes in the electronic band structure of these non-colinear antiferromagnets. The magnetic structure of Mn₃X is crucial to Weyl physics, but is still under debate due to the lack of experimental studies. To determine the structure, we report polarized neutron diffraction studies on Mn₃X (X=Sn,Ge). In Mn3Ge, a k=0 antichiral structure was determined, which naturally explains the origin of a net in-plane magnetization along the [110] direction. In Mn3Sn, an additionnal incommensurate phase was discovered and further characterized with polarization analysis. The magnetic ground state selection of Mn₃X (X=Sn,Ge) will be discussed in terms of exchange, Dzyaloshinskii-Moriya and crystal electric field interactions.