The classical Strichartz estimates for the free Schrödinger propagator have recently been substantially generalised to estimates of the formfor orthonormal systems (f j ) j of initial data in L 2 , firstly in work of Frank-Lewin-Lieb-Seiringer and later by Frank-Sabin. The primary objective is identifying the largest possible α as a function of p and q, and in contrast to the classical case, for such estimates the critical case turns out to be (p, q) = ( d+1 d , d+1 d−1 ). We consider the case of orthonormal systems (f j ) j in the homogeneous Sobolev spacesḢ s for s ∈ (0, d 2 ) and we establish the sharp value of α as a function of p, q and s, except possibly an endpoint in certain cases, at which we establish some weak-type estimates. Furthermore, at the critical case (p, q) = ( d+1 d−2s , 2s) ) for general s, we show the veracity of the desired estimates when α = p if we consider frequency localised estimates, and the failure of the (non-localised) estimates when α = p; this exhibits the difficulty of upgrading from frequency localised estimates in this context, again in contrast to the classical setting.Date: August 21, 2017. 1 A B means A ≤ CB for an appropriate constant C 1 arXiv:1708.05588v1 [math.FA]