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Structural and Physical Properties of CaFe4As3 Single Crystals

We report the synthesis, and structural and physical properties of CaFe4As3 single crystals. Needle-like single crystals of CaFe4As3 were grown out of Sn flux and the compound adopts an orthorhombic structure as determined by X-ray diffraction measurements. Electrical, magnetic, and thermal properties indicate that the system undergoes two successive phase transitions occurring at TN1 ~ 90 K and TN2 ~ 26 K. At TN1, electrical resistivities (ρ(b) and ρ(ac)) are enhanced while magnetic susceptibilities (χ(b) and χ(ac)) are reduced in both directions parallel and perpendicular to the b-axis, consistent with the scenario of antiferromagnetic spin-density-wave formation. At TN2, specific heat reveals a slope change, and χ(ac) decreases sharply but χ(b) has a clear jump before it decreases again with decreasing temperature. Remarkably, both ρ(b) and ρ(ac) decrease sharply with thermal hysteresis, indicating the first-order nature of the phase transition at TN2. At low temperatures, ρ(b) and ρ(ac) can be described by ρ = ρ0 + AT^α(ρ0, A, and α are constants). Interestingly, these constants vary with applied magnetic field. The ground state of CaFe4As3 is discussed.