  We report high pressure studies on the C-type antiferromagnetic semiconductor
EuTe2 up to 36.0 GPa. A structural transition from the I4/mcm to C2/m space
group is identified at ~16 GPa. Superconductivity is discovered above ~5 GPa in
both the I4/mcm and C2/m space groups. In the low-pressure phase (< 16 GPa),
the antiferromagnetic transition temperature is enhanced with increasing
pressure due to the enhanced magnetic exchange interactions. Magnetoresistance
measurements indicate an interplay between the local moments of Eu2+ and the
conduction electrons of Te 5p orbits. The upper critical field of the
superconductivity is well above the Pauli limit. Across the structural
transition to the high-pressure phase (> 16 GPa), EuTe2 becomes nonmagnetic and
the superconducting transition temperature evolves smoothly with the upper
critical field below the Pauli limit. Therefore, the high upper critical field
of EuTe2 in the low-pressure phase is due to the exchange field compensation
effect of the Eu magnetic order and the superconductivity in both structures
may arise in the framework of the BCS theory.
