The full three-dimensional dispersion of the bands, Fermi velocities, and effective masses are measured with angle-resolved photoemission spectroscopy and compared to first-principles calculations. The band structure by density-functional theory underestimates the slope of the bands and the trigonal warping effect. Including electron-electron correlation on the level of the GW approximation, however, yields remarkable improvement in the vicinity of the Fermi level. This demonstrates the breakdown of the independent electron picture in semimetallic graphite and points toward a pronounced role of electron correlation for the interpretation of transport experiments and double-resonant Raman scattering for a wide range of carbon based materials. Recently graphene has been investigated as a prototype system to address basic questions of quantum mechanics [1-3] (relativistic Dirac fermions) as well as for high speed semimetal field effect transistors in emerging nanoelectronic devices [4]. Many of these results are based on its peculiar electronic properties, i.e., an isotropic and linear dispersion close to the Fermi level (E F ). In low dimensional and strongly anisotropic systems correlation effects play a crucial role in understanding and describing the electronic band structure. Kinks in the quasiparticle (QP) dispersions and lifetimes were observed and interpreted as band renormalization due to electron-phonon [5] and electron-plasmon [6] interactions and band-structure effects [7]. Its electronic properties are also very sensitive to stacking and the number of layers [8]. In bilayer graphene a gap that could be tuned by doping was observed [9]. For few-layer graphene, the parent compound, graphite, is the key to understanding these new phenomena. Interlayer coupling in an AB stacking sequence leads to the formation of electron and hole pockets responsible for the semimetallic character in graphite. The linear dispersion is broken and only if we have an AA stacking the linear dispersion remains. Nevertheless, at the H point of graphite [2] the band dispersion is close to linear and has been interpreted as Dirac-fermion-like. Much less is known about the quantitative description of electron-electron correlations in these graphitic systems. Angle-resolved photoemission (ARPES) studies indicated that local density approximation (LDA) gives a dispersion that is too flat and a scaling has to be applied in order to fit the experimental dispersion of few-layer graphene and graphite. [15] for Raman scattering in graphene and graphite. Furthermore, it is important to know the exact k z dispersion, because it is responsible for the conductivity perpendicular to the graphene layers.In this Letter we report on a combined ARPES and theoretical ab initio QP study of the three-dimensional band structure and the Fermi surface in graphite single crystals. ARPES is best for studying correlations since it probes the complex self-energy function which contains the electronic interactions. We elucidate the full electronic QP disper...

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Sponges are probably the earliest branching animals, and their fossil record dates back to the Precambrian. Identifying their skeletal structure and composition is thus a crucial step in improving our understanding of the early evolution of metazoans. Here, we present the discovery of 505–million-year-old chitin, found in exceptionally well preserved Vauxia gracilenta sponges from the Middle Cambrian Burgess Shale. Our new findings indicate that, given the right fossilization conditions, chitin is stable for much longer than previously suspected. The preservation of chitin in these fossils opens new avenues for research into other ancient fossil groups.