On the non-vanishing of Shalika newvectors at the identity

Let π be an irreducible admissible unitary ψ-generic representation of the non-archimedean general linear group GL _2n (F ), which admits an (η, ψ)-Shalika model S ^η (π). In this paper, we show the non-vanishing of all non-zero Shalika newvectors (formula presented) at the identity (formula presented) matrix (formula presented), if η is unramified. This complements the anal-ogous result for Whittaker newvectors, which can be read off the formulae established independently by Miyauchi in [Miy14] and the second named author in [Mat13].