NOVELTY - A proton-conducting organic compound comprising at least 5 optionally fused, aromatic moieties and having degree of crystallinity of at least 30% is new.    USE - As proton-conducting compound in proton-conducting material and in fuel cell; in electrode materials, as polyelectrolyte and/or as an additive for fuel cell applications (claimed); and for electrodes and/or membrane-electrode units.    ADVANTAGE - The compound has degree of crystallinity of at least 30 (preferably at least 50, especially at least 70, particularly at least 90)%; a melting point of at least 100 degrees C; proton conductivity of at least 10-3 S/cm, when measured at 95% RH at 25 degrees C; and has electron conductivity of at least 1 S/cm. The proton-conducting organic materials can be applied at elevated temperatures; have improved properties i.e. very high proton conductivity which is constant over a broad temperature range (preferably -20 to 250, especially 20-200, particularly 100-160) degrees C; very good mechanical properties i.e. high durability and high stability; and low water solubility. The material is obtained in a cheap and simple manner and allows for cheap and simple processing. The material increases proton mobility by self-assembly and pre-organization concept. The proton conducting material has proton conductivity of at least 10-3 (preferably at least 5x 10-2, especially at least 5x 10-1) S/cm. The electron conductivity of compound is at least 1 (preferably at least 5, especially at least 10, particularly at least 25) S/cm. The material provides high and constant proton conductivity.    DETAILED DESCRIPTION - A proton-conducting organic compound of formula R'1(R2)m(R3)n (I'), where the compound comprises at least 5, optionally fused, aromatic moieties; and has a degree of crystallinity of at least 30% is new.    R'1=optionally fused 1-200C aromatic, cyclic or polycyclic moiety, able to have 3 to 60 substituents (preferably groups of formulae (II) and/or (III) and/or (IV) and/or (V) and/or (VI) and/or (VII) and/or (VIII) and/or (IX) and/or (X) and/or (XI) and/or (XII));    R2=a group comprising at least one phosphonic acid moiety;    R3=H, halogen atom, or 1-60C group;    m=3-60;    n=0 to 57;    m+n=3 to 60;    R=the position of the substituents R2 and/or R3.    INDEPENDENT CLAIMS are included for the following:    (1) a proton-conducting material having a degree of crystallinity of at least 30%, comprising at least one organic compound of formula R1(R2)m(R3)n (I) and crystal water. The compound comprises at least 4, optionally fused, aromatic moieties; and    (2) a fuel cell comprising the new compound (I') or the material.    R1=optionally fused 1-200C aromatic, cyclic or polycyclic moiety, able to have 3 to 60 substituents.