We obtain a representation formula for the derivative of the spectral shift
function ξ(λ;B,ϵ) related to the operators H0(B,ϵ)=(Dx−By)2+Dy2+ϵx and H(B,ϵ)=H0(B,ϵ)+V(x,y),B>0,ϵ>0. We establish a limiting absorption principle
for H(B,ϵ) and an estimate O(ϵn−2) for
ξ′(λ;B,ϵ), provided λ∈/σ(Q), where $Q =
(D_x - By)^2 + D_y^2 + V(x,y).