  In the R$\_{3}$Ga$\_{5}$SiO$\_{14}$ compounds, the network R of rare earth
cations form well separated planes of corner sharing triangles topologically
equivalent to a kagom\'e lattice. Powder samples and single crystals with R =
Nd and Pr were prepared and magnetostatic measurements were performed under
magnetic field up to 10 T in the temperature range from 1.6 K to 400 K.
Analysis of the magnetic susceptibility at the high temperatures where only the
quadrupolar term of the crystal electric field prevails, suggests that the Nd
and Pr magnetic moments can be modeled as coplanar elliptic rotators
perpendicular to the three fold axis of the crystal structure that interact
antiferromagnetically. Nonetheless, a disordered phase that can be ascribed to
geometric frustration persists down to the lowest temperature which is about 25
times smaller than the energy scale for the exchange interactions.
