  We studied the magnetoresistivity of the AM2B2 and A3Rh8B6 (A = Ca, Sr; M =
Rh, Ir) compounds within the ranges 1.8<=T<=300 K and 0<=H<=50 kOe. The
zero-field resistivity {\rho}0(T) is metallic and follows closely the
Bloch-Gr\"uneisen description. A positive, nonsaturating, and dominantly
linear-in-H magnetoresistivity was observed in all samples, including the ones
with a superconducting ground state. Such {\Delta}{\rho}T(H)/{\rho}T(0),
reaching 1200% in favorable cases, was found to be much stronger for the AM2B2
compounds and to decrease with temperature as well as when Ca is replaced by
Sr, or Rh is replaced by Ir. Finally, the general features of the observed
magnetoresistivity will be discussed in terms of the Abrikosov model for the
linear magnetoresistivity in inhomogeneous materials.
