  The rapidly expanding class of quantum materials known as {\emph{topological
semimetals}} (TSM) display unique transport properties, including a striking
dependence of resistivity on applied magnetic field, that are of great interest
for both scientific and technological reasons. However, experimental signatures
that can identify or discern the dominant mechanism and connect to available
theories are scarce. Here we present the magnetic susceptibility ($\chi$), the
tangent of the Hall angle ($\tan\theta_H$) along with magnetoresistance in four
different non-magnetic semimetals with high mobilities, NbP, TaP, NbSb$_2$ and
TaSb$_2$, all of which exhibit non-saturating large MR. We find that the
distinctly different temperature dependences, $\chi(T)$ and the values of
$\tan\theta_H$ in phosphides and antimonates serve as empirical criteria to
sort the MR from different origins: NbP and TaP being uncompensated semimetals
with linear dispersion, in which the non-saturating magnetoresistance arises
due to guiding center motion, while NbSb$_2$ and TaSb$_2$ being {\it
compensated} semimetals, with a magnetoresistance emerging from nearly perfect
charge compensation of two quadratic bands. Our results illustrate how a
combination of magnetotransport and susceptibility measurements may be used to
categorize the increasingly ubiquitous non-saturating large magnetoresistance
in TSMs.
