We report observation of reflection high-energy positron diffraction (RHEPD) at the Si(l 1 1) surface using an electrostatic positron beam. The improvement of the beam (i.e., reduction of beam energy spread) was critical to obtaining the higher-order diffraction spots. We could observe the first Lane zone, which was not seen in our previous work. This allows us to study the surface Debye temperature. The obtained rocking curve represents the enhancement of the fourth Bragg peak, as expected from diffraction theory, in addition to previously confirmed total reflection and the first Bragg peak. (C) 2002 Elsevier Science B.V. All rights reserved.