  Deep Inelastic Neutron Scattering measurements on liquid $^3$He-$^4$He
mixtures in the normal phase have been performed on the VESUVIO spectrometer at
the ISIS pulsed neutron source at exchanged wavevectors of about $q \simeq
120.0$ \AA$^{-1}$. The neutron Compton profiles J(y) of the mixtures were
measured along the $T=1.96$ K isotherm for $^3$He concentrations, $x$, ranging
from 0.1 to 1.0 at saturated vapour pressures. Values of kinetic energies,
$<T>$, of $^3$He and $^4$He atoms as a function of $x$, $<T >(x)$, were
extracted from the second moment of J(y). The present determinations of $<T
>(x)$ confirm previous experimental findings for both isotopes and, in the case
of $^3$He, a substantial disagreement with theory is found. In particular $<T
>(x)$ for the $^3$He atoms is found to be independent of concentration yielding
a value $<T >_3(x=0.1)\simeq 12 K $, much lower than the value suggested by the
most recent theoretical estimates of approximately 19 K .
