  We report progress in computing and analyzing all tree amplitudes in ABJM
theory. Inspired by the isomorphism between the orthogonal Grassmannian and the
pure spinor geometries, we adopt a new gauge, called u-gauge, for evaluating
the orthogonal Grassmannian integral for ABJM amplitudes. We carry out the
integral explicitly for the 8-point amplitude and obtain the complete
supersymmetric amplitude. The physical and spurious poles arise from the
integral as expected from on-shell diagrams. We also derive a double scalar
soft theorem of ABJM amplitudes and verify it for known amplitudes.
