  The magnetic properties of CoSi single crystals have been measured in a range
of temperatures $T = 5.5 - 450$ K and magnetic field strengths $H \leq 11$ kOe.
A comparison of the results for crystals grown in various laboratories allowed
the temperature dependence of magnetic susceptibility $\chi(T) = M(T)/H$ to be
determined for a hypothetical "ideal" (free of magnetic impurities and defects)
CoSi crystal. The susceptibility of this ideal crystal in the entire
temperature range exhibits a diamagnetic character. The $\chi(T)$ value
significantly increases in absolute value with decreasing temperature and
exhibits saturation at the lowest temperatures studied. For real CoSi crystals
of four types, paramagnetic contributions to the susceptibility have been
evaluated and nonlinear (with respect to the field) contributions to the
magnetization have been separated and taken into account in the calculations of
$\chi(T)$.
