The new compounds RE4O4[AsO4]Cl (RE = La, Pr, Nd, Sm, Eu, Gd) were synthesised by solid state reaction via a salt flux route and investigated by HRTEM, SAED, and single crystal X-ray diffraction. The samples crystallise with a tetragonal cell, space group P4(2)/mnm and Z= 2. Their crystal structure consists of an alternation of [RE4O4](4+) and [ClAsO4](4-) layers. The [RE4O4](4+) layer contains ORE4/4 tetrahedra which share common edges. The anions AsO43- and Cl- are located between these layers in disordered manner. SAED and HRTEM experiments confirmed this structural model and enabled us to propose an ordered model for the [CIAsO4](4-) layers. (C) 2014 Elsevier Ltd. All rights reserved.