I'd like to change the global opacity of my mesh but I don't want him to be transparent with himself.

For example in this screenshot I don't want to see the cross on the left. It's weird because it looks like it's working for the two other cross.

My material :

new THREE.MeshPhysicalMaterial({
    color: '#FF0',
    transparent:true,
    opacity:0.5,
    metalness:1
})

Does anyone know what I'm missing ? Thanks