  We present a new formula for all single trace tree amplitudes in four
dimensional super Yang-Mills coupled to Einstein supergravity. Like the
Cachazo-He-Yuan formula, our expression is supported on solutions of the
scattering equations, but with momenta written in terms of spinor helicity
variables. Supersymmetry and parity are both manifest. In the pure gravity and
pure Yang-Mills sectors, it reduces to the known twistor-string formulae. We
show that the formula behaves correctly under factorization and sketch how
these amplitudes may be obtained from a four-dimensional (ambi)twistor string.
