Powershell 3.0: Creating AD account issue with UserPrincipalName

Hello everyone,

I am new here and my knowledge about Powershell is still under improving process so if my question would look as trifle please forgive! :)

I have created script with params thanks to which I am able to create AD account in domain but I do not why UserPrincipalName is being avoided each time after execution...

param ($GivenName,$Surname,$Name,$SAMAccountName,$PrincipalName, `
$patch="OU=Users,OU=PL-Warsaw,OU=CEE,DC=alico,DC=corp", $ObjectCategory="CN=Person,CN=Schema,CN=Configuration,DC=alico,DC=corp",$Description,$Department,$StreetAddress,`
$TelephoneNumber,$Office,$Title,$help)


function pomoc()
{

$tekst=@"

To jest tekst pomocy do skryptu tworzenia konta uzytkownika:

- GivenName: Tutaj podajemy imie uzytkownika np. "Tomasz"
- SurName: Tutaj podajemy nazwisko np. "Bartnicki"
- SAMAccountName: Tutaj podajemy nazwe domenowa uzytkownika np. "tbartnicki"
- PrincipalName: Tutaj podajemy login uzytkownika np. "tbartnicki@comain.com"
- Name: Tego parametru nie podajemy, zostaniemy o niego poproszeni zaraz po wywolaniu skryptu
i nalezy wtedy podac imie i nazwisko np. "Tomasz Bartnicki"
- Description: Tutaj podajemy opis stanowiska
- Street: Tutaj podajemy adres miejsca pracy np. "xxx26"
- Departament: Tutaj podajemy nazwe departamentu np. "MIS"
- TelephoneNumber: Tutaj podajemy numer telefonu np. "+48226543214"
- Office: Tutaj podajemy nazwe firmy np. "Company"
- Title: Tutaj podajemy stanowisko pracy np. "Administrator aplikacji"

Zatem przykladowa komenda wywolania skryptu tworzenia konta bedzie:

ADUser.ps1 -GivenName User -Surname Testing -SAMAccountName utesting -UserPrincipalName utesting@domain.com -Description Administrator...

Koniec

"@
$tekst
exit
}

if ($help)
{
    Write-Host "Pobieranie pomocy..."; pomoc}


New-ADUser -GivenName $GivenName -Surname $Surname -SamAccountName $SAMAccountName -UserPrincipalName $PrincipalName `
-Path $patch -Description $Description -Department $Department `
-StreetAddress $StreetAddress -OfficePhone $TelephoneNumber -Office $Office -Title $Title

The executed command works fine but due to unknown reason "userprincipalname" remains blank.

So I inserted one command more to the script:

$Identity=Read-host "Type the login"
$PrincipalName=Read-Host "Type domain login"

Set-ADUser -Identity $Identity -UserPrincipalName $PrincipalName

And after then the account is finally completed.

But I do not want to use Set-ADUser - how Can I use properties declared earlier to be insterted to $identity and $PrincipleName and avoid typing SAMAccountName and PrincipleName ?

Thank you in advance!