Bounds for Siegel Modular Forms of genus 2 modulo $p$
  Sturm obtained the bounds for the number of the first Fourier coefficients of elliptic modular form $f$ to determine vanishing of $f$ modulo a prime $p$. In this paper, we study analogues of Sturm's bound for Siegel modular forms of genus 2. We show the resulting bound is sharp. As an application, we study congruences involving Atkin's $U(p)$-operator for the Fourier coefficients of Siegel mdoular forms of genus 2. 
Dohoon Choi, YoungJu Choie, Toshiyuki Kikuta
math.NT