How to concatenate columns with Laravel 4 Eloquent?

I have a table called tenantdetails which contains

Tenant_Id | First_Name | Last_Name | ........

and I want to retrieve First_Name and Last Name as one column via the concatenation function of MySQL. So I write in my controller as follows

$tenants = Tenant::orderBy('First_Name')->lists('CONCAT(`First_Name`," ",`Last_Name`)','Tenant_Id');

But results the following error:

 SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error 
 in your SQL syntax; check the manual that corresponds to your MySQL server
 version for the right syntax to use near '`," ",`First_Name`)`, 
 `Id` from `tenantdetails` order by `F' at line 1 

 (SQL: select `CONCAT(`First_Name`," ",`Last_Name`)`, `Id` 
 from `tenantdetails` order by `First_Name` asc).

How can we avoid the backticks while calling a function of MySQL in Laravel Eloquent. I am interested only in Eloquent (not in fluent query). Thanks in advance.

Update

Thanks to @Andreyco for helping me. We can achieve this in a more elegant way using Laravel models, as below:

In our model:

public function getTenantFullNameAttribute()
{
    return $this->attributes['First_Name'] .' '. $this->attributes['Last_Name'];
}

and in our controller:

$tenants = Tenant::orderBy('First_Name')->get();
$tenants = $tenants->lists('TenantFullName', 'Tenant_Id');

Answer

Tenant::select('Tenant_Id', DB::raw('CONCAT(First_Name, " ", Last_Name) AS full_name'))
    ->orderBy('First_Name')
    ->lists('full_name', 'Tenant_Id');