  The magnetic structure of CsCo2Se2 was investigated using single-crystal
neutron diffraction technique. An antiferromagnetic transition with the
propagation vector (0,0,1) was observed at T_N = 78 K. The Co magnetic moment
0.772(6) {\mu}_B at 10 K pointing in the basal plane couples ferromagnetically
in the plane which stacks antiferromagnetically along the c direction. Tuning
and suppressing the interplane antiferromagnetic interaction may be crucial to
induce the material to a superconducting state.
