Woocommerce: Add text to price in cart but not to Related Products

I’ve added the text “kg*” after the price on the product page. However, it also adds the additional text to the price of the Related Products below. How do I exclude the price being added to the Related Products? I want to add the text only to the price of the product.

add_filter( 'woocommerce_get_price_html', 'hellblau_kg_nach_preis', 100, 2  );
function hellblau_kg_nach_preis($price){
    if( is_single() ) { 
        global $product;
        $weight = $product->get_weight();    
        return $price . ' / ' . $weight . ' kg*';
    }
    return $price;
}

I’ve tried several things like if( is_single() && ! RELATED-PRODUCTS ) without success.