Thanks. I will use this workarround.
'btnMapa
btnMapaIcon.Initialize("btnMapa")
btnMapa.Initialize("btnMapa")
btnMapaIcon.Typeface = FA.FontAwesomeTypeface
btnMapaIcon.Color = Colors.RGB(62, 99, 143)
btnMapa.Color = Colors.RGB(62, 99, 143)
btnMapaIcon.TextSize = 24
btnMapa.TextSize = 16
btnMapaIcon.TextColor = Colors.White
btnMapa.TextColor = Colors.White
btnMapaIcon.Text = FA.GetFontAwesomeIconByName("fa-globe")
btnMapa.Text = "Mapa"
Activity.AddView(btnMapa, 30dip, 70dip, 100%x - 60dip, 70dip)
Activity.AddView(btnMapaIcon, 30dip, 70dip, 60dip, 70dip)