A pseudo-binary system of epsilon-(Mn1-xFex)(3+delta)Ge (hexagonal DO1
9 type structure) has a collinear antiferromagnetic phase in a composi
tion range near x = 0.2 at low temperatures. A field-induced transitio
n from the collinear antiferromagnetic phase to the triangular antifer
romagnetic phase (higher temperature phase) was observed in high field
s of about 100 kOe.