Structural Evidence of Charge Density Waves in the Series of Molecular Conductors and Superconductors: TTF(M(dmit) 2 ) 2 (M = Pd, Ni)

We present an x-ray study at ambient pressure of the metal complexes TTF(Pd(dmit) 2 ) 2 and TTF(Ni(dmit) 2 ) 2 as a function of temperature. At room temperature one-dimensional (1D) fluctuations are observed under the form of diffuse lines on the x-ray patterns. The Ni-derivative exhibits one type of scattering which condenses below about 40 K into satellite reflections. The Pd-derivative shows two kinds of scattering which condense into satellite reflections, respectively, at T 1 ≈ 150 K and T 2 ≈ 105 K. These observations provide evidence of charge density wave instabilities related to the 1D electronic anisotropy of these materials, and which compete with superconductivity under pressure.