Incommensurate structure and the superconducting properties of the organic superconductor (MDT-ST)(I$\mathsf{_{3})_{0.417}}$

The charge-transfer degree and the superconducting properties of the organic superconductor (MDT-ST)I$_{1+\delta }$ have been studied [ MDT-ST: 5$H$-2-(1,3-dithiol-2-ylidene)-1,3-diselena-4,6-dithiapentalene] . The Raman spectrum and the x-ray oscillation photograph show that the polyiodide chain is composed of I$_{3}^{-}$, which is incommensurate to the donor lattice. The chemical composition is determined to be (MDT-ST)(I$_{3})_{0.417}$. The upper critical fields are within the Clogston-Chandrasekhar paramagnetic limit in all directions, and the coherence lengths are longer than the thickness of the conducting sheet. Key words. Organic superconductor – incommensurate crystal – upper critical field.