use symbol with exponents Mathematica

Question

I want to use as a symbol \xi^a to create a list with the symbol \xi^0, \xi^1, \xi^2 and \xi^3.

I tried to use Symbolize to create \xi^a. I think it doesn't understand that I want [Xi]^i as a variable and not a power...

Symbolize[NotationTemplateTag[\[Xi]^a]];
Symbolize[NotationTemplateTag[\[Xi]^0]];
Symbolize[NotationTemplateTag[\[Xi]^1]];
Symbolize[NotationTemplateTag[\[Xi]^2]];
Symbolize[NotationTemplateTag[\[Xi]^3]];
\[Xi]^a = {\[Xi]^0, \[Xi]^1, \[Xi]^2, \[Xi]^3}

It gives me : {1, [Xi], [Xi]^2, [Xi]^3}