  The metamagnetic transitions in single-crystal rare-earth nickel borocarbide
HoNi_{2}B_{2}C and ErNi_{2}B_{2}C have been studied at 1.9 K with a Quantum
Design torque magnetometer. The critical fields of the transitions depend
crucially on the angle between applied field and the easy axis [110] for
HoNi_2B_2C and [100] for ErNi_2B_2C. Torque measurements have been made while
changing angular direction of the magnetic field (parallel to basal tetragonal
ab-planes) in a wide angular range (more than two quadrants). The results are
used not only to check and refine the angular diagram for metamagnetic
transitions in these compounnds, but also to find new features of the
metamagnetic states. Among new results for the Ho borocarbide are the influence
of a multidomain antiferromagnetic state, and ``frustrated'' behavior of the
magnetic system for field directions close to the hard axis [100]. Torque
measurements of the Er borocarbide clearly show that the sequence of
metamagnetic transitions with increasing field (and the corresponding number of
metamagnetic states) depends on the angular direction of the magnetic field
relative to the easy axis.
