Perfectoid overconvergent Siegel modular forms and the overconvergent Eichler--Shimura morphism

The aim of this paper is twofold. We first present a construction of overconvergent automorphic sheaves for Siegel modular forms by generalising the perfectoid method, originally introduced by Chojecki--Hansen--Johansson for automorphic forms on compact Shimura curves over $mathbf{Q}$. These sheaves are then verified to be isomorphic to the ones introduced by Andreatta--Iovita--Pilloni. Secondly, we establish an overconvergent Eichler--Shimura morphism for Siegel modular forms, generalising the result of Andreatta--Iovita--Stevens for elliptic modular forms.