  MnP and FeP are show complex magnetic spiral states with geometric phase
contributions to the anomalous Hall effect and the topological Hall effect,
where both have thermoelectric Nernst counterparts. We use state of the art
first principle calculations to show that both Hall and Nernst effects are
enhanced in MnP and FeP due to the temperature dependent magnetic texture. At
ambient pressure the inversion breaking crystals shows a transition from a
double-spiral helimagnetic phase to a topologically trivial magnetic phase.
This helimagnetic structure is determined by exchange frustration and the
Dzyaloshinskii-Moriya interaction. In the presence of an external magnetic
field the magnetic structure transforms into a fan-like phase with a finite
spin chirality that gives rise to an effective magnetic field on the order
$\sim$1 T. The topological Hall and Nernst effect from this field are
comparable or larger to tightly-wound skyrmion systems. Lastly, we show that
the topological effects are strongly dependent on the Fermi surface topology,
which has strong variations and even sign changes for similar magnetic
textures.
