Get TierPrices on home page/outside product view

Question

I made a .phtml block which should display the lowest price by the parameter sku

{{block type="core/template" sku="theproductsku" template="getlowestprice.phtml"}}

and the getlowestprice.phtml looks like this

$_product = Mage::getModel('catalog/product')->loadByAttribute('sku',$this->sku);
$price=$prod->getPrice();

While getting price works just fine, getting the tier price like I used in product view doesnt work:

$prices = $this->getTierPrices($_product);

($prices equals NULL)

Is there any workaround to get tier prices outside product view?