  Within the RCo$_2$ family of compounds, a structural distortion linked with
the onset of magnetic ordering around the critical temperature can be observed.
One of the less explored RCo$_2$ compounds is TmCo$_2$ probably due to its low
Curie temperature. Exceptionally this compound, given its position at the end
of the ferrimagnetic series, shows discrepancies in the ordering of the Co
sub-lattice because of a weak Weiss molecular field. In this paper we focus on
the structural distortion in TmCo$_2$, which appears together with the magnetic
ordering around the critical temperature of $T_{C}\sim3.6$~K. Poly-crystals as
well as single-crystals of TmCo$_2$ were used in our experiments. For both
kinds of samples we observed the same type of the rhombohedral distortion along
the [111] direction from the cubic Fd$\bar{3}$m to R$\bar{3}$m space group. The
relation between observed magnetic and structural properties in this compound
is discussed.
