Can't sort by meta_key because it's stored in serialized array

I’ve been trying to spit out a list of my properties and order them by city, but it seems I can’t do this because it’s stored in some sort of serialized array. Can you tell me how I can sort by a custom field?

The following does not work…

$args = array(
    'post_type' => 'properties',
    'meta_key' => 'pd_city',
    'orderby' => 'meta_value',
    'order' => 'DESC',
    'posts_per_page' => 5
);
$the_query = new WP_Query( $args );

https://wordpress.org/plugins/post-meta/