A single-crystal X-ray diffraction analysis has been performed on LiEr(PO3)(4) prepared by the flux method. The compound crystallizes in the monoclinic system with space group C2/c and cell parameters: a = 16.262(2), b = 7.032(l), c = 9.549(2) angstrom and beta = 125.95(1)degrees. The crystal structure was refined based on 1272 independent reflections with I > 2 sigma(I). Final values of the reliability factors were improven considerably: R(F-2) = 0.0180 and wR(F-2) = 0.0490. The LiEr(PO3)(4) structure is characterized by infinite chains (PO3)(n), extending parallel to the b direction. The ErO8 dodecahedra and LiO4 tetrahedra alternate on two-fold axes in the middle of four (PO3)(n) chains. The vibrational study by infrared absorption spectroscopy is reported. (C) 2005 Elsevier Ltd. All rights reserved.