PauliEta[I] represents a two-component Pauli spinor η\etaη, while PauliEta[-I] stands for η†\eta^{\dagger }η†.
PauliEta[I]
PauliEta[-I]
Overview, PauliXi.
η\etaη
η†\eta ^{\dagger }η†
PauliEta[-I] . SIS[p] . PauliXi[I] % // ComplexConjugate
η†.(σˉ⋅p‾).ξ\eta ^{\dagger }.\left(\bar{\sigma }\cdot \overline{p}\right).\xiη†.(σˉ⋅p).ξ
ξ†.(σˉ⋅p‾).η\xi ^{\dagger }.\left(\bar{\sigma }\cdot \overline{p}\right).\etaξ†.(σˉ⋅p).η