  Tree amplitudes of 10D supersymmetric Yang-Mills theory (SYM) and 11D
supergravity (SUGRA) are collected in multi-particle counterparts of analytic
on-shell superfields. These have essentially the same form as their chiral 4D
counterparts describing ${\cal N}=4$ SYM and ${\cal N}=8$ SUGRA, but with
components dependent on a different set of bosonic variables. These are the
D=10 and D=11 spinor helicity variables, the set of which includes the spinor
frame variable (Lorentz harmonics) and a scalar density, and generalized
homogeneous coordinates of the coset $\frac{SO(D-2)}{SO(D-4)\otimes U(1)}$
(internal harmonics).
  We present an especially convenient parametrization of the spinor harmonics
(Lorentz covariant gauge fixed with the use of an auxiliary gauge symmetry) and
use this to find (a gauge fixed version of) the 3-point tree superamplitudes of
10D SYM and 11D SUGRA which generalize the 4 dimensional anti-MHV
superamplitudes.
