Here, by applying a comprehensive approach including magnetic, transport measurements, ARPES band structure measurements, DFT calculations, and analytical theory consideration, we unveil the puzzling origin of the negative isotropic magnetoresistance in the highly anisotropic semimetals, particularly, ${\mathrm{Eu}}_2{\mathrm{Sn}}_2{\mathrm{As}}_2$ with AFM ordering of Eu atoms. The isotropic magnetoresistance developing along with the magnetization changes up to the complete spin polarization field has been reported in several experimental studies, though its theoretical explanation has been lacking. Recently, we proposed a theoretical mechanism based on the exchange energy splitting to describe the observed magnetoresistance in layered AFM compounds by exchange splitting of the electron energy levels and by confining the electron wave functions with different spin projection in the vicinity of the respective magnetic layer. In this paper we present more detailed experimental studies of the negative magnetoresistance with several samples of ${\mathrm{EuSn}}_2{\mathrm{As}}_2$ in order to test the universal character of the exchange splitting mechanism. We also substantiate the proposed theory by comparing it with magnetotransport data, with ARPES measurements of the energy band structure, and with DFT energy spectrum calculations.

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• Antiferromagnetism
• Electrical conductivity
• Magnetic phase transitions
• Magnetoresistance
• Magnetotransport
• Antiferromagnets
• Dirac semimetal
• Magnetic multilayers
• Semimetals
• van der Waals systems
• Angle-resolved photoemission spectroscopy
• Boltzmann theory
• Density functional theory
• Magnetization measurements
• Resistivity measurements
• X-ray diffraction