The groups of Prof. Toshio Hyodo, Institute of Materials Structure Science, KEK; Dr. Atsuo Kawasuso, Principal Researcher, Advanced Science Research Center, Japan Atomic Energy Agency; and Associate Prof. Iwao Matsuda, The Institute for Solid State Physics, The University of Tokyo studied the structure of silicene, which consists of a single layer of silicon deposited on a single-crystal silver (Ag) surface, using reflection high-energy positron diffraction (RHEPD). This technique can accurately determine atomic positions on the top surface of a crystal. These groups experimentally confirmed for the first time that silicene has an buckling structure unlike planar graphene, which consists of a flat single layer of carbon atoms.