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The development of new sensitive multifunctional materials, which simultaneously react both to mechanical pressure and a constant magnetic field, is one of challenges of the modern materials science. In order to create materials that can simultaneously possess extrinsic piezoresistance and magnetoresistance, polymer composites based on La 0.7 Sr 0.3 MnO 3 (LSMO) and low density polyethylene (LDPE) of composition (100-x)LSMO / xLDPE at x = 7, 8, 9, 12, 15, 17, 18, 22 mass percent have been synthesized in this work. The composites have been synthesized at 170°C and a pressure of 50 MPa in the presence of hydrocarbons. The phase composition of the obtained samples has been studied by X-ray diffraction and infrared spectroscopy. Electric, piezoresistance and magnetoresistance properties of the samples have been studied. It has been found out that with increasing concentration of polyethylene, the electrical resistance of the samples also increases. It has been established that the percolation threshold of the composites is about 13 wt.% of polyethylene. A maximum is observed in the dependence of the electrical resistance of the samples on the uniaxial pressure at a concentration of polyethylene near the percolation threshold at x =15 wt.%. Samples with concentration of x =15 wt.% of low density polyethylene show extrinsic piezoresistance of about 17 % in the pressure range 0 -270 kPa. Significant hysteresis is observed when considering the dependence of piezoresistance on pressure for all samples. The pressure sensitivity for a sample of 85 %LSMO / 15 %LDPE reaches 8.40 mΩ / Pa. The maximum values of the negative isotropic tunnel magnetoresistance of the composites 88 %LSMO / 12 %LDPE have values of about 2 % in a 15 kOe magnetic field. We believe that the materials studied in the paper could be useful for designing multifunctional biosensors of mechanical pressure and constant magnetic field.

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