  In this report, structural, electronic, magnetic and transport properties of
quaternary Heusler alloys CoRuMnGe and CoRuVZ (Z = Al, Ga) are investigated.
All the three alloys are found to crystallize in cubic structure. CoRuMnGe
exhibits L2$_1$ structure whereas, the other two alloys have B2-type disorder.
For CoRuMnGe and CoRuVGa, the experimental magnetic moments are in close
agreement with the theory as well as those predicted by the Slater-Pauling
rule, while for CoRuVAl, a relatively large deviation is seen. The reduction in
the moment in case of CoRuVAl possibly arises due to the anti-site disorder
between Co and Ru sites as well as V and Al sites. Among these alloys, CoRuMnGe
has the highest T$\mathrm{_C}$ of 560 K. Resistivity variation with temperature
reflects the half-metallic nature in CoRuMnGe alloy. CoRuVAl shows metallic
character in both paramagnetic and ferromagnetic states, whereas the
temperature dependence of resistivity for CoRuVGa is quite unusual. In the last
system, $\rho$ vs. T curve shows an anomaly in the form of a maximum and a
region of negative temperature coefficient of resistivity (TCR) in the
magnetically ordered state. The ab initio calculations predict nearly
half-metallic ferromagnetic state with high spin polarization of 91, 89 and 93
\% for CoRuMnGe, CoRuVAl and CoRuVGa respectively. To investigate the
electronic properties of the experimentally observed structure, the Co-Ru swap
disordered structures of CoRuMnGe alloy are also simulated and it is found that
the disordered structures retain half-metallic nature, high spin polarization
with almost same magnetic moment as in the ideal structure. Nearly
half-metallic character, high T$\mathrm{_C}$ and high spin polarization make
CoRuMnGe alloy promising for room temperature spintronic applications.
