  In-plane longitudinal and transverse thermoelectric phenomena in two parent
compounds of iron-based superconductors are studied. Namely, the Seebeck (S)
and Nernst (n) coefficients were measured in the temperature range 10 - 300 K
for BaFe2As2 and CaFe2As2 single crystals that were detwinned in-situ. The
thermoelectric response shows sizeable anisotropy in the spin density wave
state (SDW) for both compounds, while some dissimilarities in the vicinity of
the SDW transition can be attributed to the different nature of the phase
change in BaFe2As2 and CaFe2As2. Temperature dependences of S and n can be
described within a two-band model that contains a contribution from highly
mobile, probably Dirac, electrons. The Dirac band seems to be rather isotropic,
whereas most of the anisotropy in the transport phenomena could be attributed
to "regular" hole-like charge carriers. We also observe that the off-diagonal
element of the Peltier tensor axy is not the same for the a and b orthorhombic
axes, which indicates that the widely used Mott formula is not applicable to
the SDW state of iron-based superconductors.
