This paper reviews structural phase transitions of BaSi
2 at high pressures and high temperatures, and electrical resistivity measurements of two quenched high-pressure, high-temperature phases and a stable phase at ambient conditions. In situ x-ray diffraction measurements reveal that BaSi
2 has three high pressure, high temperature phases: trigonal, cubic and an additional phase, at pressures up to 7 GPa and temperatures up to 1300 K. All of the high pressure, high temperature phases can be quenched at ambient conditions. The electrical resistivity measurements of trigonal, cubic and orthorhombic BaSi
2, a stable phase at ambient conditions, at 1 atm show that the electrical resistivity strongly depends on their crystal structure: orthorhombic and cubic BaSi
2 are n-type semiconductors, and trigonal BaSi
2 is a hole metal that shows superconductivity with an onset temperature of 6.8 K.
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