  Bulk magnetic, X-ray and neutron diffraction measurements were performed on
polycrystalline Tb14Ag51 in the temperature range from 1.5 K to room
temperature. Its chemical Gd14Ag51 type structure corresponds to space group
P6/m. Combined with group theoretical symmetry analysis, we show that the
magnetic structure of this intermetallic compound is of a new k = (1/3,1/3,0)
type with three magnetic Tb sublattices ordering simultaneously below TN =
27.5(5) K according to the combined irreducible representations tau4 and tau6.
Here we present a general analysis of possible magnetic A ordering for k =
(1/3,1/3,0) in A14B51 compounds.
