  The effects of chemical disorder on the transport properties of the
spin-filter material CrVTiAl are investigated experimentally and theoretically.
Synchrotron X-ray diffraction experiments on bulk CrVTiAl and the associated
Rietveld analysis indicate that the crystal structure consists primarily of a
mixture of a partially ordered B2 phase, a fully disordered A2 phase and a
small component of an ordered L2\textsubscript{1} or Y phase. High temperature
resistivity measurements confirm the existence of a band gap. First-principles,
all-electron, self-consistent electronic structure computations show that the
chemically disordered A2 and B2 phases are metallic, while the spin-filter
properties of the ideal Y-type phase are preserved in the presence of
L2\textsubscript{1} disorder. The Hall coefficient is found to decrease with
increasing temperature, similar to the measured increase in the conductivity,
indicating the presence of thermally activated semiconductor-like carriers.
