function contributors() {
global $wpdb;
$authors = $wpdb->get_results("SELECT ID, user_nicename from $wpdb->users ORDER BY display_name"); //Go get all users

 $current_category =  get_query_var('cat');
// to then get the cat name
$current_category_name = get_cat_name( $current_category);

foreach($authors as $author) {

 $fileira = get_the_author_meta('fileira', $author->ID); //get the value of fileira custom field

if(strtolower($fileira) == strtolower($current_category_name)) {
 //if the fileira custom field value is the same as category name
//the users with current category ID/name on fileira custom field should appear

echo "<li>"."<a href=\"".get_bloginfo('url')."/?author=".$author->ID."\">".get_avatar($author->ID)."</a>";
echo '<div>'."<a href=\"".get_bloginfo('url')."/?author=".$author->ID."\">".the_author_meta('display_name', $author->ID)."</a>"."</div>"."</li>";
echo '<div>'.$fileira."</div>"."</li>"; //show fileira value
}

}
}

contributors();