Change header on pages displaying taxonomy items

You need to change the code that currently displays that header, so that it doesn’t display the default title when it’s on this taxonomy.

You can detect if you are on a taxonomy page with the is_tax() function, and then you could do something like this:

$term_array = get_term_by( 'slug', get_query_var( 'term' ), 'materia' );
                echo $term_array->name;