<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>Fe</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:msub> <mml:mi>Mg</mml:mi> <mml:mn>3</mml:mn> </mml:msub> </mml:mrow> </mml:math> stabilization and solid-solution preliminary observations in the Fe-Mg system at high pressure and high temperature