Main theme over riding 'templatepath' in child theme?

Hello all,

Searches haven’t brought me any clear insight on this.

So, I am trying to add category specific “single.php” pages in my child theme.

Basic process I am following is putting the following in single.php file, then creating the referred files.

<?php

$post = $wp_query->post;

if ( in_category('3') ) {

  include(TEMPLATEPATH. 'C:/wamp/www/wordpress/wp-content/themes/My-Child-Theme/single-articles.php'); } 

elseif ( in_category('8') ) {

  include(TEMPLATEPATH. 'C:/wamp/www/wordpress/wp-content/themes/My-Child-Theme/single-sys.php'); } 

else {

  include(TEMPLATEPATH. 'C:/wamp/www/wordpress/wp-content/themes/My-Child-Theme/single-default.php');

}

?>

I dropped this in, to return the path and it always returns the main theme directory. I thought trying to guide the path with the full directory would fix it, but to no avail.

<?php echo TEMPLATEPATH; ?>

If anyone has a link or idea for where to go next to resolve this it would be appreciated!

Thanks for your time,

Nimo1