  Co2MnAl has been predicted to have Weyl points near Fermi level which is
expected to give rise to exotic transverse transport properties such as large
anomalous Hall(AHE) and Nernst effects(ANE) due to large Berry curvature. In
this study, the effect of Fermi level position and atomic ordering on AHE and
ANE in Co2MnAl1-xSix were studied systematically. The Co2MnAl film keeps
B2-disordred structure regardless of annealing temperature, which results in
much smaller anomalous Hall conductivity sigma_xy and transverse Peltier
coefficient sigma_xy than those calculated for L21-ordered Co2MnAl. Our newly
performed calculation of sigma_xy with taking B2 disordering into account well
reproduces experimental result, thus it was concluded that Berry curvature
originating from Weyl points is largely reduced by B2 disordering. It was also
revealed Al substitution with Si shifts the position of Fermi level and
improves the L21-atomic ordering largely, leading to strong enhancement of
sigma_xy, which also agreed with our theoretical calculation. The highest
thermopower of ANE of 6.1uV, which is comparable to the recent reports for
Co2MnGa, was observed for Co2MnAl0.63Si0.37 because of dominant contribution of
sigma_xy. This study clearly shows the importance of both Fermi level tuning
and high atomic ordering for obtaining the effect of topological feature in
Co-based Heusler alloys on transverse transport properties.
