C-13 NMR MEASUREMENTS OF THE HIGH-MAGNETIC-FIELD, LOW-TEMPERATURE PHASES OF (TMTTF)(2)PF6

We report NMR spectroscopy of C-13-labeled TMTTF molecules in high-mag netic fields that established the field-temperature phase diagram for (TMTTF)(2)PF6. The dimerized spin-Peierls (D) ground state is driven t o an incommensurate (I) phase for fields B > B-c = 19.1 +/- 0.1 T. In the I phase, the staggered component of the magnetization is much larg er for (TMTTF)(2)PF6 than it is for CuGeO3. On approaching the transit ion to the D phase from higher temperatures, we observe an unusual bro adening of the NMR spectrum which is probably from extrinsic sources a nd related to pinning of solitonlike excitations in individual chains.